T6100: Added NAT migration from IP/Netmask to Network/Netmask
Added NAT migration from IP/Netmask to Network/Netmask.
In 1.3 allowed using IP/Netmask in Nat rules.
In 1.4 and 1.5 it is prohibited. Allowed Network/Netmask.
(cherry picked from commit 52c02ade031f165da18e6fd0542f3952f2cc9bb6)