FlightData screen's Action tab button reordering

As discussed with some of the Flight Test crew at 3DR we should probably re-group the buttons on the Action tab. I've taken a shot at reorganising it. The thinking behind the re-ordering was:
1. buttons on a single line should all have some relation to each other. So the top line is flight mode line (with the exception of Auto which is in it's own group below. The 2nd line is the Auto related actions. The 3rd line is Arming related buttons.
2. buttons should not be too close together so that people don't accidentally hit them. This is why I put arming at the bottom because if it was at the top it might be possible to arm/disarm while the user tries to change tabs.
3. reduced the "Change Speed" default value to 10 (10m/s I guess) because 100 seemed way too high! I removed the ChangeAlt drop-down because it's not supported in AC3.2 anyway and Tridge and I don't really have a clear idea of what it should be doing anyway.


Start by locating Mission Planner's FlightData screen and its Action tab, then compare the current button layout with the attached mockup. Done means the buttons are regrouped with safer spacing, Change Speed defaults to 10, and the unsupported ChangeAlt control is removed.

Written by the indexing model from the issue text.