Added new features to script window

[lloyddewit]

This PR is draft, not yet ready to review.

Fixes #6645
Fixes #6541
Fixes (partly) #4932

Fixes (potentially):

• Improving the script window? #7632
• The Edit > Script dialogue executes twice #7435
• Bug when trying to run in the Window script a regular expression containing hashtag #7014
• Improve parsing of multi-line R script #6744
• Find/Replace dialogue changing strings on its own #6720
• Command that doesn't work in script file #6683
• Script that causes problems in R-Instat #6619
• Running multiple commands from the script window #6178
• Allow '=' to be used instead of '<-' in the script window #5807
• Script window - extra bracket added? #4444
• Executing commands from the script file #4381
• Message when running the script file #4216
• Redo from script. #3567
• Refill parser from previous R command #3566

[lloyddewit]

@rdstern @Patowhiz
This PR uses the 'ScintillaNET' package. This package provides more advanced editor features than the Windows Forms 'TextBox' control. This allows us to add features such as syntax highlighting and line numbers. However, I don't know how well 'ScintillaNET' would run in the R-Instat Linux version.
Who would be the best person to test this PR branch in Linux?

[lloyddewit]

@rdstern
I added some of the key editor features requested by @lilyclements :

• Fixed width font
• Syntax highlighting
• Line numbers
• Ensured that typical editor functions like cut/copy/paste/undo/redo/select etc. all work in a standard way with standard keyboard shortcuts
• Improved right mouse click menu

If you agree, then I think this would be a good time to merge. I would implement the next improvements in a new PR.
Please could you test?

Possible next improvements:

• make 'ctrl-enter' execute the R statement at the cursor (rather than just the line), this should fix the current bugs with multi-line statements
• add tabbed windows
• add auto close brackets, close quotes and indentation
• add reformat option to tidy indentation and line breaks (including splitting long lines)
• tidy up file open/save/save-as functionality
• add auto-complete
• find/replace dialog
• display cursor row/column at bottom of editor
• ensure commands on R-Instat 'Edit' menu work as expected in script window
• ensure controls translate to French and other languages
• update help files
• test on Unix

Do you have a preference regarding which I should implement first (I can provide time estimates if needed)?

If you want to compare against RStudio, then the RStudio editor functionality is described below.

https://support.rstudio.com/hc/en-us/articles/200484448-Editing-and-Executing-Code-in-the-RStudio-IDE
https://support.rstudio.com/hc/en-us/articles/200710523-Navigating-Code-in-the-RStudio-IDE
https://support.rstudio.com/hc/en-us/articles/205273297-Code-Completion-in-the-RStudio-IDE
https://support.rstudio.com/hc/en-us/articles/200484568-Code-Folding-and-Sections-in-the-RStudio-IDE

[rdstern]

@lloyddewit this is looking very nice indeed. I have searched for something to complain about, but it seems to work fine!

[rdstern]

@lloyddewit I don't have strong views about the order of the items in the new pull request. So very happy for you to decide on the most efficient logical order.

[lloyddewit]

This is just a note for myself that I could test the script window with code from issue #7889.

[N-thony]

txtScript.Copy() on line 204? to make it consistent with line 211 and get rid of CopyText()?

[lloyddewit]

Thanks, I understand your point.
Copytext() is also called by frmMain. Therefore, we cannot delete it.
If we don't call CopyText() on line 204, then we also need to call EnableDisableButtons() which adds an extra line of duplicated code.
So on balance, I'll leave the above code unchanged. I hope that's OK.