New >>=  operator for the ChFrame and ChFrameMoving . This supersedes the %= operator, that will be considered deprecated. This is more coherent with the fact that there is already a binary operator >>.
This is part of a process for harminizing the Chrono::Engine API, where all 'reverse order' transformations (in quaternions, frames, etc. ) will be represented with the >> operator, as well as the direct transformations are represented by * operator.
Better comments for quaternion constructors.
New constructor for ChMatrix33 , from axis and angle of rotation. Keeps things shorter, less typing when creating rotation matrices.
New method to set a rotation matrix from angle of rotation and angle of rotation. This previously required too much typing, typically one had to create a quaternion, set it from angle and axis, and create the matrix from the quaternion.
IMPORTANT change in ChQuaternion API.  Previously, the * operator was used for doing element-by-element product, that was almost useless. We assume that no one used it. So, now we use the * operator to perform the true quaternion operator, as it was done with % operator previously.
The old % operator is made deprecated, then.
Also, we added the >> operator and its in-place >>= operator, to do the product in 'specular' order, i.e. A*B is the same as B >> A.
This makes things more coherent through the Chrono::ENgine API because the * operator represents the same 'meaning' also for ChFrame, ChFrameMoving, etc. , that is, it 'concatenates' transformations in direct order (in this cases, for quaternion it concatenates rotations). Similarly, the >> operator provides a concatenation of transformations in specular order.
The % operator for quaternion product  is considered deprecated, the * operator should be used instead.
There are many places in the code where % was used, they might be promoted to * quaternion product in future.
Python support for new >> and >>= operators in quaternions.
Merge branch 'develop' of https://github.com/projectchrono/chrono into develop