Add a launch lockout

A send to APM with a valid mission needs to be done before a launch
using the button is allowed. This lockout is reset on disconnect.
Disconnect should be done between each flight as it resets this failsafe
and splits up the tlog files into one per flight.
Colored Buttons on flight screen

Added colors to the buttons on the flight screen. The dangerous buttons,
arm/dismarm and stabilize are also on the left side of the screen so
they are harder to accidently activate.
Merge pull request #3 from PaulLoizeaux/LaunchLockout

Add a launch lockout