Removed some duplicate code.
All current behavior should stay the same.

Merged GotoTreeBookmark into the almost identical GetObjectIsMarked:
> Added a bool parameter to control the behavior of GetObjectIsMarked
> There was only 1 call to GotoTreeBookmark in the whole code.
   Replaced it with a call to GetObjectIsMarked

Change-Id: I3594512d0ff425ab2bd5636845d0e703dee85d52
Reviewed-on: https://gerrit.libreoffice.org/17505Reviewed-by: jan iversen <jani@documentfoundation.org>
Tested-by: jan iversen <jani@documentfoundation.org>