Add lua as sub-module to support translation.

This makes the Lua scripts first-class citizen in darktable.

.gitmodules

@@ -17,3 +17,6 @@
 [submodule "src/external/LibRaw"]
 	path = src/external/LibRaw
 	url = https://github.com/LibRaw/LibRaw.git
+[submodule "src/external/lua-scripts"]
+	path = src/external/lua-scripts
+	url = https://github.com/darktable-org/lua-scripts.git

po/POTFILES.in

@@ -23,13 +23,13 @@ build/lib/darktable/plugins/introspection_colorbalancergb.c
 build/lib/darktable/plugins/introspection_colorchecker.c
 build/lib/darktable/plugins/introspection_colorcontrast.c
 build/lib/darktable/plugins/introspection_colorcorrection.c
+build/lib/darktable/plugins/introspection_colorequal.c
 build/lib/darktable/plugins/introspection_colorin.c
 build/lib/darktable/plugins/introspection_colorize.c
 build/lib/darktable/plugins/introspection_colormapping.c
 build/lib/darktable/plugins/introspection_colorout.c
 build/lib/darktable/plugins/introspection_colorreconstruction.c
 build/lib/darktable/plugins/introspection_colortransfer.c
-build/lib/darktable/plugins/introspection_colorequal.c
 build/lib/darktable/plugins/introspection_colorzones.c
 build/lib/darktable/plugins/introspection_crop.c
 build/lib/darktable/plugins/introspection_defringe.c
@@ -94,6 +94,85 @@ build/lib/darktable/plugins/introspection_zonesystem.c
 build/share/darktable/org.darktable.darktable.desktop.in
 data/org.darktable.darktable.appdata.xml.in
 data/org.darktable.darktable.desktop.in
+external/lua-scripts/contrib/AutoGrouper.lua
+external/lua-scripts/contrib/CollectHelper.lua
+external/lua-scripts/contrib/HDRMerge.lua
+external/lua-scripts/contrib/LabelsToTags.lua
+external/lua-scripts/contrib/OpenInExplorer.lua
+external/lua-scripts/contrib/RL_out_sharp.lua
+external/lua-scripts/contrib/auto_snapshot.lua
+external/lua-scripts/contrib/autostyle.lua
+external/lua-scripts/contrib/change_group_leader.lua
+external/lua-scripts/contrib/clear_GPS.lua
+external/lua-scripts/contrib/color_profile_manager.lua
+external/lua-scripts/contrib/copy_attach_detach_tags.lua
+external/lua-scripts/contrib/cr2hdr.lua
+external/lua-scripts/contrib/cycle_group_leader.lua
+external/lua-scripts/contrib/dbmaint.lua
+external/lua-scripts/contrib/enfuseAdvanced.lua
+external/lua-scripts/contrib/exportLUT.lua
+external/lua-scripts/contrib/ext_editor.lua
+external/lua-scripts/contrib/face_recognition.lua
+external/lua-scripts/contrib/fujifilm_dynamic_range.lua
+external/lua-scripts/contrib/fujifilm_ratings.lua
+external/lua-scripts/contrib/geoJSON_export.lua
+external/lua-scripts/contrib/geoToolbox.lua
+external/lua-scripts/contrib/gimp.lua
+external/lua-scripts/contrib/gpx_export.lua
+external/lua-scripts/contrib/harmonic_armature_guide.lua
+external/lua-scripts/contrib/hif_group_leader.lua
+external/lua-scripts/contrib/hugin.lua
+external/lua-scripts/contrib/image_stack.lua
+external/lua-scripts/contrib/image_time.lua
+external/lua-scripts/contrib/jpg_group_leader.lua
+external/lua-scripts/contrib/kml_export.lua
+external/lua-scripts/contrib/passport_guide.lua
+external/lua-scripts/contrib/passport_guide_germany.lua
+external/lua-scripts/contrib/pdf_slideshow.lua
+external/lua-scripts/contrib/photils.lua
+external/lua-scripts/contrib/quicktag.lua
+external/lua-scripts/contrib/rate_group.lua
+external/lua-scripts/contrib/rename-tags.lua
+external/lua-scripts/contrib/rename_images.lua
+external/lua-scripts/contrib/select_non_existing.lua
+external/lua-scripts/contrib/select_untagged.lua
+external/lua-scripts/contrib/slideshowMusic.lua
+external/lua-scripts/contrib/transfer_hierarchy.lua
+external/lua-scripts/contrib/video_ffmpeg.lua
+external/lua-scripts/examples/api_version.lua
+external/lua-scripts/examples/darkroom_demo.lua
+external/lua-scripts/examples/gettextExample.lua
+external/lua-scripts/examples/gui_action.lua
+external/lua-scripts/examples/hello_world.lua
+external/lua-scripts/examples/lighttable_demo.lua
+external/lua-scripts/examples/moduleExample.lua
+external/lua-scripts/examples/multi_os.lua
+external/lua-scripts/examples/panels_demo.lua
+external/lua-scripts/examples/preferenceExamples.lua
+external/lua-scripts/examples/printExamples.lua
+external/lua-scripts/examples/running_os.lua
+external/lua-scripts/examples/x-touch.lua
+external/lua-scripts/lib/dtutils.lua
+external/lua-scripts/lib/dtutils/debug.lua
+external/lua-scripts/lib/dtutils/file.lua
+external/lua-scripts/lib/dtutils/log.lua
+external/lua-scripts/lib/dtutils/string.lua
+external/lua-scripts/lib/dtutils/system.lua
+external/lua-scripts/official/check_for_updates.lua
+external/lua-scripts/official/copy_paste_metadata.lua
+external/lua-scripts/official/delete_long_tags.lua
+external/lua-scripts/official/delete_unused_tags.lua
+external/lua-scripts/official/enfuse.lua
+external/lua-scripts/official/generate_image_txt.lua
+external/lua-scripts/official/image_path_in_ui.lua
+external/lua-scripts/official/import_filter_manager.lua
+external/lua-scripts/official/import_filters.lua
+external/lua-scripts/official/save_selection.lua
+external/lua-scripts/official/selection_to_pdf.lua
+external/lua-scripts/tools/executable_manager.lua
+external/lua-scripts/tools/get_lib_manpages.lua
+external/lua-scripts/tools/get_libdoc.lua
+external/lua-scripts/tools/script_manager.lua
 src/bauhaus/bauhaus.c
 src/chart/main.c
 src/cli/main.c
@@ -219,13 +298,13 @@ src/iop/colorbalancergb.c
 src/iop/colorchecker.c
 src/iop/colorcontrast.c
 src/iop/colorcorrection.c
+src/iop/colorequal.c
 src/iop/colorin.c
 src/iop/colorize.c
 src/iop/colormapping.c
 src/iop/colorout.c
 src/iop/colorreconstruction.c
 src/iop/colortransfer.c
-src/iop/colorequal.c
 src/iop/colorzones.c
 src/iop/crop.c
 src/iop/defringe.c