Added documentation for REST API layer.

The goal of this patch is to setup infrastructure and organization
of docs in the project.

Changes:
* Added documentation for REST objects along with examples
* Added documentation for REST endpoints
* Added auto-generation of REST API docs

Note(1):
New API endpoint will not be auto-added to the docs. It is responibility
of committer to add new endpoint to the docs.

Note(2):
Usage examples still need to be added manually.

Change-Id: I080a6daba2fdb8a1a6a18087c7b3929da5b4bf1a
Merge "Added documentation for REST API layer."