Relax hash tree restrictions on forks.
Support explicit object sharing between ht forks.
Retroactively update ht snapshots.
Fix htls, route messages being sent every frame.
Reduce expectations when joining or another node lacks grant.
Add network identifier of bootstrap node to NetworkInfo.

This is the only way for new nodes to discover the netid of the
bootstrap node, should they ever need to actually talk to it.
Add fullstack test against joining via non-bootstrap node.