This adds an Application subclass to get the onCreate() method, which is
called once at the first start up of the app, before any Activity starts.
Tor is configured there to ensure it is setup before anything happens.
This also moves the "Use Tor" pref listener to a more appropriate place.
* renamed VideoInfoItem to VideoPreviewInfo
* moved streaming service-related classes into their own, new package services
* added javadoc to some classes and methods (where functionality is known well enough to explain)
* De-duplicated common fields between VideoInfo and VideoPreviewInfo by moving them into a common superclass: AbstractVideoInfo
* Removed 2 methods which only call super(), and therefore are unnecessary: PlayVideoActivity.onResume() and PlayVideoActivity.onPostCreate(Bundle)
