Added sensors to objects;
Added grasp to robot nodes;
Extended RobotIO::RobotDescription;
Allow reloading of the robot visualization if RobotDescription::KinematicStructure is chosen

Added manipulability tracking, composite diff ik, soechting nullspace constraints and an example graphical user interface in RobotViewer

This reverts commit 0e0778dc.

* also clean up cmake

Refactoring of MMM framework to SimoxUtility: Added string helpers and conversion tools, a distinguishable color lookup table e.g. for creating graphs, a rapidxml wrapper for easier parsing of xml files and moved deprecated RobotPoseDiffIK from MMMTools to VirtualRobot

Changed folder name mjcf to mujoco