Documentation according to new template provided by the Docs team

Documentation according to new template provided by the Docs team

- The Config guide is not an atonomos document, but will be scraped into a
  bigger context.

- The post install guide is not an atonomos document, but will be scraped
  into a bigger context.

- Installation instructions is an atonomos document describing details on
  how to install Fuel@OPNFV

- Build instructions is an atonomos document describing how to build Fuel@OPNFV

- Release notes

- Agreed with the community that binary image files shall be in the repo,
  as much as I hate it.

DO NOT MERGE

JIRA: FUEL-38

Change-Id: I88a93e20ef2c67a2c973147a7a1e332e3da55674
Signed-off-by: Jonas Bjurel <jonas.bjurel@ericsson.com>
(cherry picked from commit ef0b33dcc34ee38d090487eabba122ae018980a0)