Add dump directory to collect BUFR converter mapping file and an opti…

…onal Python script for each observation type (#2)

Create a dump directory with a subdirectory call mapping to collect
components necessary to convert BUFR data info IODA format for each data
type
1. mapping file 
2. Python script (if applicable)

This directory is for convert `BUFR dump` files as well as `prepBUFR`
files.

Co-authored-by: Ron McLaren <[email protected]>