core: Remove unused bookmark queries

This patch removed the unused GetBookmarkById and GetBookmarkByName
queries.

Removed in this patch:
1. The query classes.
2. The parameter classes used by the aforementioned queries.
3. The validation methods used to validate the aforementioned
   parameters.
4. The constants from VdcQueryType corresponding to the aforementioned
   queries.

Change-Id: If130d51f240beebcfdda56e8c03c9f0321100ebf
Signed-off-by: Allon Mureinik <amureini@redhat.com>