core: Remove unused GetDisksForQuotaIdQuery

GetDisksForQuotaIdQuery is not used anywhere in the code, and hence
should be removed.

This patch removes the following:
1. The GetDisksForQuotaIdQuery class
2. The GetDisksForQuotaIdParameters class used by said query
3. The GetDisksForQuotaId constant representing it in VdcQueryType
4. The getAllForQuotaId(Guid) method in DiskImageDAO (which was only
   used by the query), its implementation, and its test.
5. The GetImagesByQuotaId(UUID) stored procedure that was only used by
   the said DAO function.

Change-Id: I77f8c0a54fbcdc150234888d73a941088376ef3e
Signed-off-by: Allon Mureinik <amureini@redhat.com>