Alter UAS.cc so that it transmits MANUAL_CONTROL messages at 5Hz when no inputs have changed.
Otherwise MANUAL_CONTROL messages are still sent at the regular 50Hz. This reduces transmission bandwidth from 0.9kbps when the joystick is used continuously to 0.1kbps when it's idle.
To prevent possible issues from the last high-bandwidth message being lost and the system then not responding for .1s, the last messsage is double-transmit which should prevent those issues.
Reduced size of datatypes involved with JoystickInput class.
Most math and backend storage was floats anyways, so most of these changes just half the data copied during function calls without reducing precision.
Merge pull request #714 from Susurrus/joystick

Reduce the transmission rate of MANUAL_CONTROL messages when command inputs have not changed