Add method to write parameters on file

Add new method to ParamHelpClient and ParamHelpServer classes that allow
the user to write the current values of the specified parameters on a
text file.
Improve paramHelp library

- delete memory associated to parameters that are not linked to any user
variable
- delete the cloned ParamProxyInterfaces in ParamHelperBase::close()
- add some comments
- initialize pointers to 0 in ParamHelperBase default constructor
Implement command to save parameters on file

- remove parameter filename
- add parameter filename to rpc command "save"
- change size of kt, kv* and kc* vectors from _n to N_DOF, to match
current definition of these parameters in jointTorqueControlParams.h
- implement rpc command "save" that writes estimated parameters on text
file
- move all variables in jointTorqueControlParams.h into its namespace
- remove useless includes
- stop using interruptModule() because it could get called after close()
causing segmentation fault