Added ListBox to MoonifyControls.
Changed the way the ListBox handles index-changes.
All negative values are considered -1 (no index).
Implemented an overrideable OnSelectedIndexChanged method and collected all index-functionality in a region.
Removed keydown override in ListBox.
Implemented all methods for ListBox.ObjectCollection as required by the IList<T> interface.
Changed the default size of the ListBox (120 equals 4 lines of 30 pixels).
The parameterized constructors now also actually add objects to the inner collection.
Merge branch 'ListBox'