Updated HIL message specifications to better meet demand, added helper functions to convert between Euler, Quaternions and rotation matrices (DCM), following NASA rotation standard and originally written (as attributed) by James Goppert.
Added copy step for conversions header, reverted HIL_STATE to original state, marked it as deprecated and added HIL_STATE_QUATERNION for the intended long-term message
Merge pull request #125 from mavlink/hil_fixes

Updated HIL message specifications to better meet demand, added helper functions for quaternions