webadmin: sorting DC tabs

- Implemented sorting in data center main tab.
- Implemented sorting in data center sub tabs.
- Added comparators for the sub tabs that do not support
  server side sorting.

Change-Id: Id95272bd4594a66611c11aaa690d44d88b082b49
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1119873
Signed-off-by: Alexander Wels <awels@redhat.com>