[Major] spatial class SE3 is now CRTP. Move traits class in spatial/fwd.h as it is now used in spatial classes and joint-base

Added two minor functionalities in the python bindings

[Python] force the computations of all coefficient in the mass matrix, in the binding of computeAllTerms.

Build library only if sources are detected.

Compilation with qcc for QNX

[C++] Remove forbidden instances of typename keyword.

  - This is necessary to build with older compiler versions.
  - The keyword typename must only be used in template declarations
    and definitions and only in contexts in which dependent names can
    be used. This excludes explicit specialization declarations and
    explicit instantiation declarations (until C++11).

Add computation of CoM position, velocity and accelerations + minor ajustements

Topic/mac compatibility

[C++] Add com information in data + compute position, velocity and acceleration of CoM in the same loop + add related unittest

Implement exp and log map in C++ and expose them in Python. Still need some adjustments to be really efficient.