References #1928: Changed filter UI to use a direct manipulation paradigm via drag and drop.

(cherry picked from commit ba2e00f0e29704a2705f5e17d4d98b0400eb30c0)
References #1928: Drag handles can now be drop targets.  Fixed bugs with dragging composites.  Fixed bug with overeager model unlinking when dropping.

(cherry picked from commit 2ae297c268c0a855e2e154ff6899f20ee8db31eb)
References #1928: Fixed drag-over feedback so it works on Windows.  Improved drag-over feedback so it more accurately reports valid drop targets.  Tweaked checkboxes so they appear with a consistent background in Windows.

(cherry picked from commit 909d31fc455ccded33d5028314c3131e5d7915e2)
References #1928: Fixed bug where dragging a CompositeFilterPanel onto itself causes said panel to disappear

(cherry picked from commit 42c56c25a1f6d788284f8b915d0ff87ca2052e04)
References #1928: Adjusted font size so icons render better on Windows

(cherry picked from commit 027748bd2d6d48606403723312616b40b34b3c90)
References #1928: Added tooltips for drag/drop.  Fixed backgrounds of more checkboxes on Windows.

(cherry picked from commit 1383bbfbdff5d2a73c56c3b878cd5b26f480398f)
References #1928: Added delete button for conditions.  Removed right-click menu from drag handles.  Updated drag handle tooltips.

(cherry picked from commit 2e1ab6f709902b7cbc67c65a8980aab9c4a8bfdd)