New operators for doing transformations with mixed types ChFrame / ChFrameMoving. This was not possible explicitly in previous API and forced to promote a ChFrame to a ChFrameMoving by constructing it before doing the * or >> operation with a ChFrameMoving.
This is implemented now for both  * operator (right to left coord. transformation) and >> operator (left to right transformation).
Note that when doing  ChFrame * ChFrameMoving one could have the option of implementing either ChFrame  or ChFrameMoving as return type. I decided to return the type 'at the end' of the kinematic transformation, that is the right most in the * expressions and the leftmost in the >> expressions, so I decided that  ChFrame * ChFrameMoving  returns a ChFrameMoving , whereas  ChFrameMoving *  ChFrame  returns a ChFrame.  In most cases this fits the needs of the programmer and does not introduce too overhead as returning always the more complex type ChFrameMoving.
In future I'll add also mixed operators for ChCoordsys vs ChFrame  and ChFrameMoving.
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop