Ability to skip frames in motion detection.
The reason for this is to make it possible to reduce CPU-load if split-second motion detection is not required.
Move initializer for last_motion_score to avoid compiler warning "...zones will be initialized after ... last_motion_score ... when initialized here"
Merge remote-tracking branch 'Sune1337/motion/FrameSkip'

Conflicts:
	db/zm_update-1.27.1.sql
	web/lang/nl_nl.php