Removed the original "Boxcar" notification settings/functionality.

In 2014, Boxcar went from version 1 to version 2.   SickBeard added support for both versions.  Today,
version 1 no longer exists; version 2 is the only one that is active, available, and functional.

Technical Details:
* Removed configuration code and settings for the original "Boxcar" notification
* The internal code and setting names for what remains is still called "Boxcar2" (in order to preserve
  current settings and to keep things simple.)
* The display title for the remaining Boxcar notifications is called "Boxcar 2" to hopefully avoid
  confusion with current users.