Added pseudoinverse with Eigen::Ref parameter type.
This kind of object makes the function less generic w.r.t. its scalar type (only double are supported for now), but it allows better temporary object management and also the use of matrix blocks as argument.
After we will test it, we should see if we can keep both function (generic and Ref type) without signature collision..
Started migration to dynamic size matrices.
Currently the code still uses static size, but I will switch to dynamic matrices.
Changed skew-symmetric function to use Ref object.