Subtitles caching updates

Dylan,

I'm so sorry--I made a bunch of changes to your central server code while testing out the system, getting it to work.  Kind of a reverse code review while you were gone.

I thought I sent this pull request, but while reviewing your code I realized that what you submitted is mostly what you had before.

My suggestion is for us to sit down tomorrow with this pull request and walk through it a bit--again, kind of a reverse code review.  Are you up for that?

Sorry that things turned out a bit weird.  I went ahead and made these changes in order to try and help the user out who was looking to get subtitles working while you were gone.