Feature Request for Mission Planner - Warning for Potentially Blurry Images

#### Issue details
I use Mission Planner to generate flight plans for collecting UAS imagery for photogrammetry purposes. Mission Planner makes it very easy to generate a plan with a specified overlap based on camera parameters. However, prior to generating a mission in MP I have to do a calculation to determine whether or not my images will be blurry based on my shutter speed, aircraft speed, elevation and camera parameters. This calculation is based off of the "half-pixel rule" as suggested by Drone Mapper (https://dronemapper.com/uas_photogrammetry_processing). The half-pixel rule essentially states that, to obtain sharp imagery, the aircraft must not move more than 1/2 ground sampling distance (GSD) while the photo is being take (i.e. during the time the photo is being exposed). I believe incorporating this calculation within MP would be relatively simple as all of the parameters for the calculation are already available when creating a mission except for shutter speed. The user would input their shutter speed and this feature could provide some kind of warning if images will be blurry (i.e. aircraft will move more than 1/2 GSD during exposure time), suggesting to increase altitude or decrease speed.

The easiest way to do this calculation is to determine how far the aircraft will move during an exposure time based on speed. Then compare that value to 1/2 the GSD based on the altitude and camera parameters (focal length, image height and width in pixels, sensor pixel size).

Thank you so much for your time!

#### Platform
[ ] All
[ ] AntennaTracker
[X ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

#### Airframe type
3DR Solo

#### Hardware type
pixhawk

No files, tests, or entry points are named. Start by locating the mission-planning calculations for aircraft speed, altitude, camera parameters, and GSD, then determine where a shutter-speed input and warning could fit; done means warning when exposure movement exceeds half the GSD, with guidance to increase altitude or decrease speed.

Written by the indexing model from the issue text.