Added syslog support & configuration

- uses new CZMQ zlog class
- zbroker.cfg shows configuration options
- server/background to run in background
- else logging is copied to foreground as well as syslog

Right now we log the server start/end; we will add futher logging as needed
over time. Note that animation and tracing are still sent to the console,
as these are really for debugging and should never be used on production
code.