Feature requests: More options for exporting cache; ability to choose which transcript to load.

[SavannahJohnston]

1. It would be nice to have more options for exporting the cache than just "export all"; e.g. to have a list of videos and their cached files, and the ability to select which ones you want to export.

2. Some videos have multiple transcripts for different languages, but try as I might YCS will only load the default transcript. (And yes I clear the cache before I try.) It would be nice to be able to select which transcript you want to load, or if YCS just loaded whichever one you've selected in the captions or the transcript viewer.