fetchmail.log: fixed log management and startup permissions. Refs #2677

The logFile prop has been removed to keep consistent UI, logrotate
and daemon logfile.
Removed unused helper scripts..
fetchmail init script: check if any active account exists. Refs #2677

* Read configuration from stdin
* Removed fetchmailrc from disk
* Removed fetchmail home directory
* Use /var/run/fetchmail/ for locking
Use syslog to log messages. Refs #2677

Add timestamp to log messages, no need for special log rotation and
creation permissions.