camera: added minspeed setting

prevent filling disk while on the ground
mosaic: added hiding and unhiding of pages
mosaic: fixed sorting of thumbnails
scanner: don't merge regions if the resulting region would be too large
mosaic: fixed page after unhiding
camera: remove fullres option
geosearch: remove fullres option
scanner: merged regions get sum of areas
scanner: 3 bits per channel seems to give better results

far fewer false positives
script: startup scripts for 2014 OBC
mav_position: use TERRAIN_REPORT for camera height if possible
camera: use camera capture time 

seems more accurate than the chameleon timestamp
Bushmaster: use TERRAIN_REPORT for altitude