Implement feature to switch from left to right analog stick for walking commands

[paolo-viceconte]

A feature we could implement after the issues arose in #91 is to switch from the left to the right analog when sending walking commands.

This would require some modifications in the JoyPad module. Currently it does not exploit any parameter to switch between the sticks.

cc @prashanthr05 @isorrentino

[GiulioRomualdi]

A possibility is to change this line

https://github.com/robotology/walking-controllers/blob/75429cbbf444c92496beb863667cac0c50eb542e/src/JoypadModule/src/Module.cpp#L201