Add bandwidth limit / improve queuing

[MagnusS]

Currently the bridge forwards to all nodes and all packets are always delivered. The bandwidth is only limited by how fast the packets can be processed.

This could be extended to set an upper bandwidth limitation and add more intelligent queuing with packet drop on congestion (e.g. RED or drop-tail)

[MagnusS]

I have a slightly bit rotted branch with a bandwidth limited bridge implementation - will try to get this ready soon