Better error logging and SIGHUP catched to shutdown and power down.

Fix timing bug in the main loop.

Disable PIC timed tasks at start up.

If file '/var/lib/pipicpowerd/pwrdown' exists 'kill -s SIGHUP' can be used
to shutdown and power down the system.

The PIC internal timer is reset at power down of the Raspberry Pi. At wake
up the counter can be used to estimate the time if network or real time clock
is not available. The approximative time could be found with
'date --date="n hours m minutes"' where the 'n' and 'm' can be
calculated from the PIC internal timer.