Draft: network: (fixes #1218) make Pbb robust and skip unnecessary prefixes

The goal is to "cleanup" Pbb so that it is foolproof to use.

Things to do:

• Check that the Prefix length and the address length is matching (this will be useless at the end).
• Skip the prefixes if they are all 32 or 128 (for IPv4 and IPv6, respectively).
• Compress the prefixes in one entry if they are all identical (e.g., 10.0.0.0/24, 10.1.0.0/24).
• Move Pbb to a new module (manet-core ?).
• Use Ipv[4,6]InterfaceAddress to add/pick addresses from messages.
• Avoid unnecessary conversions to/from Address (if possible).

Having a new module for a single class is kinda odd, but Pbb is specific to MANET protocols, so it makes sense. Other MANET-specific protocols might follow, e.g., NHDP.

Some of the actual Pbb interfaces will be deprecated or just removed w/o deprecation.

Part of this MR is from !2645, please do not comment on these.