Support for Real-time Mapping.

[BjoernKellermann]

Add support for real-time mapping to AP2. [Let's use this issue as one where we can create a number of sub issues to get to the final goal]

An example work flow is :-

• send back the pictures to APM Planner,
• stitch the images,
• create tiles and
• show on map, while still flying.

To implement the above there are number of steps required

1) Implement auto-waypoint generation see #139 2) Auto download of Images see xxx 3) Image overlay see ???

[bbasso]

Björn--all of those features would be awesome, particularly downlinking of image thumbnails.

I think the easiest thing to do first would be to downlink the CAM messages so that the sensor footprints could be overlayed on the map. This would allow you to get a rough sense of overlap and coverage, which is helpful if you're mapping large areas and if it's windy.