replace the current log options

replace the current log options

 log updates|all

with

 log state changes
 log host checks
 log connection [errors]

The first two control the logging of host check results: either changes in host state only or
all checks.

The third option controls logging of connections in relay mode:
Either log all connections, or only errors.

Additionaly, errors will be logged with LOG_WARN and good connections
will be logged with LOG_INFO, so they can be differentiated in syslog.

ok and feedback from claudio@