Added description how to use config system, fixed missing copyright headers, improved example and isort CI (#125)

* Added description how to use config system related to #20.
* Added missing copyright headers
* Improve registry example to be cleaner
* Adde habitat_sim as first party lib to isort CI setup

* Made isort for CI check only

* Added badges

Asterisk for co-first author messes up alphabetical ordering in references section.

Adds documentation for habitat-api, to view the docs follow instructions in docs/README.md and view the html files from the build folder.