New Media folders that have no new files are now correctly hidden

 When the "Hide Empty Folders" option is selected, the "New Media" folder was still displaying all folders, even if they had no new media in them (just a "Clear All" option).

This hides those folders so you only have folders which have new videos in them.

A lot of the diff is actually just white space.

I also changed the oldEntires list into a HashSet so it should be faster to lookup old values when dealing with a large number of files.

I haven't broken the "New Media" functionality more than it already is...
On my old Sony Bravia, after I watch a video, I cannot watch any other video in that folder until I return to the root folder and then let it build the DLNAResources again. I *fixes* the "Clear All" option to work the same way, otherwise it was leaving empty folders in the structure until I restarted the server.