Add integrate and differentiate methods in JointModel

[jcarpent]

No description provided.

[jcarpent]

Add also random method for each joint

[jmirabel]

For the differentiate method of SO3 joints, a convention must be chosen. This convention relates to what is being modelled: the rotation group or the unit quaternions group. Each rotation is mapped to 2 quaternions.
Thus, the "difference" between two quaternions a and b can be:

• either the angle axis between a and b (the quaternion representation)
• or the angle axis that has the shortest angle, between a and b or between a and -b (the rotation representation)

In HPP, we use the rotation representation. This has several implications. The one I can think of now are:

• Equality check: a and -a must be considered as the same rotation for the whole software => two configurations q1 and q2 can be equal even if q1.isApprox (q2) is false.
• Difference and distance: use the angle axis that has the shortest angle

See https://github.com/jmirabel/hpp-model/blob/devel/src/joint-configuration.cc#L243

[jcarpent]

The second proposition is the rational one. Because, we are working on base orientation, which can be handled by many representations:

• rotation matrix (unique representation)
• quaternion, with a non-infectivity (a and -a leads to the same orientation)
• Euler angles (with a lot of drawbacks - singularities)

[fvalenza]

Solved with #141