Updates to main readme.
Add much more info to usage article.
Move simulator building to simulation's readme.
Improve assembly article.
Many fixes.
Updates in diagrams.
Support SET_ATTITUDE_TARGET, SET_ACTUATOR_CONTROL_TARGET in mavlink.
ACTUATOR_OUTPUT_STATUS is changed ACTUATOR_CONTROL_TARGET to match used message for setting motor outputs.
Add support for changing mode from mavlink.
Support automatic flights in pyflix.
Arm and disarm with gestures only: left stick right/down for arming, left/down for disarming.
Remove arming switch as it complicates arming gestures logic.
Remove MAV_CTRL_SCALE parameter as it complicates arming gestures logic, advise to decrease TILT_MAX when controlling with a smartphone.
Put some minimal thrust to motors to indicate armed state.
Rename build article to usage article, add flight instructions.
