Add a oauth1-configuration.rst and extension section to docs

The patch addresses the following:
1) Add an extensions section to the configuration.rst
2) Add the oauth-configuration.rst to the previously mentioned
section.

fixes bug: #1218722

Change-Id: I0c832d89698fc43a19408e8e7c159f09e0ec5e15
Merge "Add a oauth1-configuration.rst and extension section to docs"