[PRD-2455] Complete nova-net limitations check

Completed Nova-Network limitations checking in Nailgun. Tests added.

1) + VLANs of all networks must not be intersected to each other (all network modes) or Fixed VLAN range (VLAN manager).
2) + IP address spaces of all networks in cluster must not be intersected to each other (exception: Floating ranges can be in Public CIDR).
3) + IP address ranges inside Public and Floating networks must not be intersected to each other.
4) + Public ranges and gateway must be in one CIDR which is calculated using netmask.
5) + Public network gateway field must not be in any of Public or Floating IP ranges.
6) + Public and Floating networks are rated as a single network when they assigned to nodes' physical interfaces. So they must share one VLAN and must be assigned together to one interface.
7) + Any physical interface of any node can have not more than one assigned untagged network (exception: point 6).
8) + VLAN IDs must be in range 2, 4094. Untagged network must have VLAN ID == None.
9) + Number of Fixed networks must fit in Fixed CIDR and size of one Fixed network.
10)+ Every network group must have amount == 1 except Fixed network in case of VLAN manager.

Both providers configuration restrictions:
1) + All networks must belong to the allowed IP ranges (network of class A, B or C excluding loopback range).
2) + Network address ranges and gateway must not intersect with subnetwork address and broadcast address.

Full description of network configuration limitations:
https://etherpad.openstack.org/p/limitations-of-networking-configuration

Change-Id: Ifd5b26e4a167dcb8ec47537db1f9ea20a4ae09aa
Merge "[PRD-2455] Complete nova-net limitations check"