ChanMgr: Implement the functions needed to install a ChannelFactory and an AbstractPtMgr.
There are some questions here in the TODO pt-client comments.
This is part of #659 (closed).
@eta: In order to make it all work, I found it necessary to require Send and Sync for the returned ChannelFactories. I hope this won't conflict too much with your !886 (merged) work.