5.0.15 Released

This update fixes some more user-reported pesky bugs like "Response (last) line started with a * but next word was not a valid response like OK, BAD, etc" when connecting to certain IMAP SSL accounts. Indy Networking Library has been updated again to the latest and greatest for added stability. Save as file has had multiple bug fixes (file types list, removing illegal characters) and one new feature (remembering the filename when you change types). And I've dropped the "beta" from this version number, to clarify that this release should actually be fairly stable.

A couple minor changes to the installer too: It wasn't correctly shutting down PopTrayU during the install, and I've updated the file naming scheme to be more user-friendly/readable.