This should remove the deprecated messages spanning all over the packages relying on pinocchio and thus on eigenpy.

- Update API to follow Eigen conventions
- Add Doc
- Remove unaligned conversions

- Update API to follow Eigen conventions
- Add Doc
- Remove unaligned conversions

Correct warnings + introduce check or registration

One should register the non aligned version if needed explicitely

Fix bug in multiple dynamic link of the lib

[C++] Make PyMatrixType a singleton to avoid multiple instantiactions to avoid dynamic linking errors

Improve the packaging of EigenPy

Add Scalar template argument to UnalignedEquivalent struct.

* It allows creating unaligned equivalent of Eigen matrix using a
  different scalar type. This can be useful when matrix types use
  single precision floats, whereas Numpy matrix types use double
  precision floats by default.
* Default template argument value is Matrix D scalar type to preserve
  backward-compatibility.

Fix issue in .pc file