Implement a max communities filter match

Implement a max communities filter match

When max-communities X is set on a filterrule the filter will match when
more than X communities are present in the path. In other words
max-communities 0 means no communities are allowed and max-communities 3
limits it up to 3 communities.
There is max-communities, max-ext-communities and max-large-communities
for each of the 3 community attributes. These three max checks can be used
together.
OK tb@ job@