core: macPool per DC, db changes

* add table mac_pools — for pool data
* add table mac_pool_ranges — for each range of given pool
* add respective business entities

Change-Id: Id30f3c384ecf933daaacdbdd6542e88afb98f7ca
Bug-Url: https://bugzilla.redhat.com/1078844
Signed-off-by: Martin Mucha <mmucha@redhat.com>