Refine DisparityModule

[pattacini]

PR #22 introduced DisparityModule with the aim to take over SFM.

Now, we ought to refine the new module addressing the following points:

• Let the module load/save parameters from/to DisparityModule.ini instead of SFM.ini.
• Provide doxygen documentation as it is presently done for SFM.
• Fix the RPC API with respect to:
  • The command [x y].
  • The command Flood3D.
  • The command [uL_1 vL_1 uR_1 vR_1 ... uL_n vL_n uR_n vR_n].
  • The handling of invalid responses in terms of (0.0, 0.0, 0.0).

Be careful, the documentation is currently managed by a dedicated GitHub Action. Anyway, it'd be just a matter of filling in the modules with the corresponding doxygen as done for SFM.