Added a max_force_factor that allows to reduce the max_force_demand for every sr_controller. The parameter can be modified by publishing to the right topic
Added error message if max_force_factor received is out of the valid range (0.0, 1.0)
Merge pull request #38 from shadow-robot/F_max_force_controller_topic

Added a max_force_factor that allows to reduce the max_force_demand for ...