issue #81: initial drag and drop commit

adds very basic support for sorting of playlists with drag and drop.

can now drag a playlist to a different location in the list.  no
database support implemented so playlists will not be in this order when
app is rerun.
Issue #81: updating target index determination

target index is now determined also based on the point offset of the
mouse, this handles the case where the mouse is more than half-way
through a cell and the index reported by the List is 1 too small.
Issue #81: updating catch block
Issue #81: reverting playlist order drag and drop support in preparation for file order drag and drop
[Playlist Sorting] added initial database table alteration for sortIndex
column.
[Playlist Sorting] adding support to set initial sort indexes and
read/write indexes.
[Playlist Sorting] added UI support for sort indexes.  rows in the
playlist item table are now sorted based on the DB sort index.
[Playlist Sorting] fix for making sure all rows are sorted correctly - even those above 9 ;)
[Playlist Sorting] updating sort index column width to support up to 3 digits
[Playlist Sorting] initial, partial implementation for drag and drop
including transferable and canImport detection.  actual importing will
come next.
adding null check
refactoring PlaylistItemProperty and related classes such that
comparison, getStringValue, and other methods are easier to understand and less error
prone.
[Playlist Sorting] intermediate commit for some of the drag and drop
support.
[Playlist Sorting] alexandria refactor: moving versioning detection &
playlist item index generation to lowest level in database, made
mid-level database operations into static methods in XXXDB.java classes,
and high-level db entities remained largely untouched.
[Playlist Sorting] actual drag and drop implementation.  full support
for single, multiple, and multi (non-contiguous) item drag and drop in
playlist item list.
[Playlist Sorting] disabling drag and drop when sorting by non-index
columns or when sorting of index column is descending.
[Playlist Sorting] cleanups of TODO source tags
[Playlist Sorting] no TODO item here after all
merge from master