No longer support policy servicegroup
Show NAT tag in error message.
Reject duplicate policy_distribution_point
Fixed imperfect check for hidden and multiple NAT.
Check reversed dynamic NAT in loop
Fixed error message (broken since 7fd717)
Fixed another error message (broken since 7fd717)
Better check multi tag NAT in loop.
Add missing change of previous commit.
NAT: more tests, more robust check for hidden.
Fixed non determinism in error message.
Fixed check for single 'permit ip any any'.
Fixed handling of NAT in loops.

Current implementation is a bit fuzzy.
If host|interface is used, mark network as used.
Added return statement for PerlCritic
Attribute 'policy_distribution_point' at router.

A single global attribute at host isn't sufficient, if we have
multiple policy distribution points.

The new router attribute can additionally be defined in
'router_attributes' of area.

The global attribute is still used as default, if it is neither
defined at router nor inherited from area.
Attribute 'general_permit' at router and area.

At area, attribute is given under 'router_attributes'.
global:permit will no longer be supported in coming versions.
Rules are no longer checked for redundancy with global:permit.