Implement notification to plugins for disconnect request, connect, drop,
and close. This allows plugins to properly handle slaves and the master
server shutting down without sending messages that will get lost.
Fix log spam when the dole distribution method is used on
subspace_storage plugin. This was caused by a bogus if condition being
translated into a sensible but wrong one.
Add web_root option to the master server and use it create URLs for
resources hosted by it. This permits hosting the master server web
interface behind reverse proxy under a dedicated path.
Hornwitser