Integrate Website's Watched List

Refactor ChangeWatched to avoid duplication, extend it to update the
website's watched list, and change its signature to require watched
parameter and conform to naming convention.
Add plugin menu option to browse and modify the website's watched and to
watch lists.
Add context menus to add items to watched and to watch list.
Add feature, enabled by a new setting, that adds movies from website's
watch list to the XBMC library along with regular subscription updates.
Modify create_item and build_listitem to accept the name of the calling
function as a parameter.  This allows special treatment for certain
menus.
Post-Rebase Changes

Add new modes to enumerator.
Missed a couple enumeration swaps

Missed a couple enumeration swaps
One Little Extra D

Fixed MODES.CH_WATCH call.
Merge pull request #4 from bryandam/website-to-watch

Integrate Website's To Watch List
Making changes to prep for 2.5.0 merge
remove unnecessary init; set remove items to constant to avoid future
bug
Added set_totals to get_towatch
Updated changelog with bdam's changes
Fix Show Trailer in context menu when it no actual url existed
Merge branch 'website-to-watch' into 2.5.0