Affinity and antiaffinity implementation.

	- RO descriptor now support "availability_zone" tag in the VNFC descriptor.
	- RO database extend table vms table to include availability_zone.
	- In case a VNF requires more  zones than available in the datacenter, an error message of instantiation failure will be issued and the usual rollback procedure will  start.
	- In case a VDU does not include availability tag, it will be treated as normal, following the default scheduling policy in the VIM.

Change-Id: I335a0db6fa232953f655a598351dd7e7bbb97785
Signed-off-by: mirabal <leonardo.mirabal@altran.com>