We need a --server option to cwipc_forward

[jackjansen]

This would be a server mode, which starts streaming compressed point clouds as soon as it is connected to, and that can stream to multiple connections.

We can then fire this up on the external server, and it can be used as a point cloud source by anyone.

Point clouds need to be "retimestamped".

[jackjansen]

Actual implementation was a change to the cwipc_forward implementation, so it can accept multiple connections, and feed to those in parallel.

When multiple connections are active (but only then) the --nodrop semantics are slightly lowered, so that if one connection is blocked this does not starve the other connections (i.e. point clouds for the blocked connection will be dropped).