this allows for testing taildragger takeoffs in FBWA mode

Added Pitch axis flipping. You must be pushing forward or back 3° to make it flip in Pitch axis or it will flip in the default roll axis.
Added some extra throttle control to maintain altitude
removed the CH7 ability to exit Flip mode. It will exit only if completing flip or user aborts with control sticks.

this saves a tiny amount of time by removing the memory copy of a
Vector3f

fixes pull #1320

thanks Arthur!

this is the start of multi-core aware code

this avoids suspending timers when transferring data between main
thread and SPI read thread

reference to rc_1, rc2 are replaced with constant updates during
acro_run

TradHeli: Add pointer for pilot roll/pitch inputs to attitude_control constructor. To be used for flybar passthrough.

AC_AttitudeControl_Heli: Create Flybar Passthrough flag which will be used for control pass-through.

the EKF check works reliably but attempts to check the inertial nav for
errors has not been successful.  I could not find a way to reliably
catch flyaways without also introducing false positives (and thus
unwanted LANDings)

use a single time base in all code