Add tests and docs to RNDF implementation in Maliput

[Agustin Alba Chicar]

We need to add unit tests and docs (Doxygen compliant) to the code in RNDF for Maliput.

Let's focus in similar cases as implemented in Monolane / Dragway and then apply custom tests for our implementation.

[Agustin Alba Chicar]

Current tests and docs are being developed here: https://github.com/ekumenlabs/drake/tree/rndf/Add_tests_and_docs

[Agustin Alba Chicar]

Already merged branch https://github.com/ekumenlabs/drake/tree/rndf/Add_tests_and_docs into https://github.com/ekumenlabs/drake/tree/Issue/RNDF_Maliput_Implementation.

Finished docs and tests.