Little changes to wbi

- add check on PWM motor control  and force/torque sensor reading for
simulator (simulator does not implement pwm motor control and F/T
sensors)
- add function globalToLocalIcubId() to convert iCub joint local ids to
iCub joint global ids
Big changes to paramHelp library

- fundamental change to paramHelp library: replace ParamDescription with
ParamProxy (the main difference being that ParamProxy manages also the
memory linked to the parameter)
- update locomotionControl, locomotionPlanner and
motorFrictionExcitation modules accordingly
- implement motorFrictionExcitation module and test it on simulation
Merge branch 'master' into paramHelpExtension
Integrate new paramHelp lib in jointTorqueCtrl
Fix warnings