Simplify cmake files

In the future, it will be useful to remove this dependency.

Eigen::Index fails on Travis.

It is a good practice to remove all warnings to:
1/ ease the reading when implementing a new functionnality.
2/ avoid nasty bugs due to the version of the compiler fixing coding
mistakes in a different way.

[joint-posture-task] Fix bug (function isn't supposed to return anyth…

[upd] Updated tsid with the latest version of pinocchio

same name for function and a variable in the function (may create bug/confusion)

[robot-wrapper] Fix bug in mass matrix: copy upper triangular part to lower triangular part (before this it was set to zero)

[robot-wrapper] BUG FIX: compute center of mass acceleration in computeAllTerms (before it was not computed so we were introducing random number in the CoM task)

[eigquadprog-fast] In DEBUG, in case a constraint is not verified, set the status flag to ERROR (even if the solver said the problem has been solved)

[task-com-equality] Fix little bugs in methods to get pos/vel references and errors, and in method to get desired acceleration