Free OBS scene migration and verification 2.0b

As we only save copies, not the original OBS JSON files, it is reasonable to use same name plus a time stamp.

This version fixes issues with that time stamp in formats that use / or \ in their date formats - now entirely omitting any date formats, just using the format as in 2021.11.4.15.39.59

Version 2.0a supports

migration of files for
ffmpeg_source
image_source
obs_stinger_transition

migration of files and folders for
vlc_source
slideshow

Any file can be individually excluded from the migration - and so can entire directories

As stinger transitions are not a source, but are an item on their own and as I have never worked with them mysself, they slipped me. Thanks to shariqmushir for the hint.

Faster file copies and minor bug fixes with some videos not playing correctly

For a selective migration (that is: not all media files are to be copied, e.g. if you have a shared video folder, but want to to migrate the other files that all come from somehere into a new clean directory) Version 1.7 adds the capability to select all, none or "all but"...

Version 1.6 fixes a bug when renaming the new scene collection within the JSON file. It may have occured that a copy (new JSON file) showed up as a duplicate in the OBS scene collection list, because the rename within the JSON file failed in older versions.