Clean up, law and order

[cmastalli]

Hi guys,

This repository is very messy and it's really important to have it in a very good shape. I proposed few and simple actions regarding my concerns:

1. Removed all legacy information regarding robcogen. You guys aren't use it, and nobody needs this in the world.
2. By default configuration the package should not depend on private repos (i.e. dls_gazebo_interface)
3. For point 2, I suggest to have a tag for activating it which you use inside the DLS framework.
4. Released the dls-gazebo environments, if you don't want it then remove the dependency too (as point 2 & 3)

Feel free to add further comments or discussion.

Sincerely,
Carlos

PD: I would like to include this repository for benchmarking in optimal control software
@fabrizioromanelli @mfocchi @orsoromeo @graiola