Make timer_cam execute at the same time every day

[frederikheld]

Currently timer_cam intervals are the pause between the end of a shot and the start of the next shot. This does not account for the time taking the shot and uploading it takes. This is why shots are shifting in time from day to day. To make time lapse videos it would be better to have them taken at the same time every day (e.g. to see how sunrise and sunset are shifting).

Desired: Add config key that allows to configure a time from the full hour/minute at which the shot will be taken. Follow same approach as cron!