webadmin: Added shared MAC pools to configure dialog

Added a left tab in the dialog, when selected the main tab is
populated with shared MAC pools configured in the system. Shared pools
may be added, edited and removed.

Change-Id: Idabfa4e2abd3c9f0b4af0d28f00a27aa92a6552f
Signed-off-by: Lior Vernia <lvernia@redhat.com>