Update to follow style guide

Update to follow style guide

The Python Style guide recommends the following:

  # with overline, for parts
  * with overline, for chapters
  =, for sections
  -, for subsections
  ^, for subsubsections
  ", for paragraphs

Update the getting-started-guide and openstack-guide and documentation
guide to use parts and chapters. We should be following this project
structure:

docs/index.rst                 -> entry point
docs/____-guide/index.rst      -> part
docs/____-guide/<chapter>.rst  -> chapter

In the ____-guide/index.rst we use the # with overline at the very top
of the file to determine that it is a part and then within each chapter
file we start the document with a section using * with overline to
denote that it's the chapter heading and then everything in the rest of
the chapter should use:

  =, for sections
  -, for subsections
  ^, for subsubsections
  ", for paragraphs

Change-Id: I4429eecc17d2e667c1f00236f9a57bc9a9028e29
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>