Update documentation

[ipa-rmb]

In order to have a general overview of the squirrel software and be more efficient during the integration meetings, our software should be properly documented. On one hand, with installation and execution instructions and, on the other hand, with a software architecture diagram to see the interconnections and dependencies between the modules. It is not necessary a diagram per node, only the most important nodes that subscribe or publish topics used by other components.

The squirrel_recommender package holds the templates and a small tutorial about how to create the diagram https://github.com/squirrel-project/squirrel_recommender#Documentation-and-Templates (2.Documentation and Templates). Please use these templates to create your documentation.