[Idea] File selector, by default, only looks for 'valid' files

[CodyCBakerPhD]

For the source data selection step for each interface, we usually know what the supported or common file suffixes are for that format (if a file based format) and likewise the folder structure required by the interface if it's a folder-based format

So it would be cool if the file selector, when pointed to a large folder with a bunch of files, filtered out all the ones not one of the designated suffixes

This would require a small addition to NeuroConv to actually write down that suffix relationship as a class attribute on each interface, similar to how we handle keywords right now