- based on https://git.eclipse.org/r/#/c/80289/
- fixes issues in bugzilla comment 14
- #1 & #2 - same bug
- #3 - expands first level of moved tree by default
- #4 - added remove button (in addition as is in context menu) and
removal seems to work
- tree is now properly expanded and new category preselected when "New
Category" (top level or nested) is created 

Change-Id: Ic29b08e1214dbb5a5bb62a3f106883ec50f1682a
Signed-off-by: Martin Karpisek <martin.karpisek@gmail.com>