meta: Split meta handling into to seperate classes.

This also renames the update-meta into update-icvpn-meta and
let all icvpn depending parts depend on the newly created class.
bird6: refactor bird6 configuration

Merge mesh/community specific tables into one mesh table.
Filter all local accessable networks, e.g. the mesh networks.
Later is not functional at this state, since the part for
generation of filter rules is not implemented, yet.
Merge remote-tracking branch 'sargon/local-meta-routing' into local-meta-routing
transport commit