ManualControl: add an expo parameter for rate mode

The implementation is based on linearly interpolation from 0 to
100% between x and x^3 of the input (-1,1) and does not change the
rate for the extreme sticks.  Based on discussion here

http://www.rcgroups.com/forums/showthread.php?t=452369&page=3
Add HTML page for new system alarm code enhancement: StateEstimation
Git issue #943

Signed-off-by: cGiesen <info@klick-punkte.info>
Update the error messages.
Thanks to kenz
Merge pull request #945 from cGiesen/next

Add HTML page for new system alarm code enhancement: StateEstimation
Improved error code message to be consistent with the one for
the accelerometer queue.
Merge pull request #872 from TauLabs/rate_expo

ManualControl: add an expo parameter for rate mode
[libKML]: Version bump.