Fix bug concerning sort and drag

Bug: Original select element is not always sorted correctly to match
displayed order of selected items because optionLink data gets
corrupted.

Fix: To reference received element, use class which already exists on
dragged elements. Don't add new class to all sorted/dragged elements,
especially since it never gets removed from sorted elements.
Fix a bug that was re-introduced with last commit

Remove `ui-draggable` class when adding items to selected list so the
class can be used to uniquely identify a received item when dragging
from available list.
Clean up inconsistent indendation and whitespace

Clean up stray space introduced in last commit, and clean up other
whitespace issues at the same time. Indent with tabs rather than spaces
because that is style used in jQuery core, and bulk of file already
uses tabs. Use spaces to align combined var statements.
Merge pull request #14 from toxalot/bugfix-sort-drag

Fix bug concerning sort and drag, plus whitespace cleanup. Thanks @toxalot!