fixing pause bug, cleanup

* fixing a bug when you pause the current photo shoot, and resume
later, that the modified exposure time (reciprocity/schwarzschildt
effect) can be wrong. fix: save the time also on the eeprom and restore
it when resuming

* cleanup of older unused code
* removing a digital write on pin 4 that used to be a status LED, but
is not anymore but one pin of the servo. could have caused problems