Fix some comments.
Merge branch 'master' of https://github.com/simbody/simbody
Refactor assembler headers and source to separate out assembly conditions.
Add some missing overrides.
Initial checkin of OrientationSensors. This is untested code not yet ready to run. But it does compile.
Add the OrientationSensors header file so it will come with Simbody.h.
Fix sign error in gradient.
Add ExampleIMUTracking to test & demo new OrientationSensors assembly condition.
Tilted the head IMU in the example to make sure that non-bodyframe IMU orientation works.
Add missing documentation for Rotation::convertRotationToQuaternion() and convertRotationToAngleAxis().
Merge pull request #239 from simbody/feature-orientation-sensor-for-Assembler

Add orientation sensor (IMU) as an assembly condition for IK