Module loading update for logging support.

Partial support of future logging system. Module loading had to be
changed because we will require thread_local socket to publish
log message. This setup task shall not fall on each module init,
so the zModuleManager handles it.
Add Logger Module.

Add a logger module (extremely basic for now) that bind a
subscriber socket at "inproc://log-sink".

ModuleLoader code initialize the thread_local socket (a publisher)
for each module so they can talk to the logger module.