v1.5.3 master

* Add:  index.php: Current Activity now supports music tracks
* Add:  index.php: Current Activity now reports if a user is "buffering"
* Change: index.php: Current Activity CSS modifications
* Change: global: date columns in all tables are no longer restricted to
"/" delimiters
* Add:  settings.php: Date/Time options modal
* Fix:  global: broken platform image link would appear if client source
was reported as Plex/Web (Unknown Browser)