The current top page of heat-dashboard doc is a bit tricky.
The content of installation is duplicated, for example.
This commit revisit the document structure.
* Drop installation instruction from README
* Drop meaningless indices and tables (which are not working)
* Move DevStack setup to the contributor document
* Merge installation_contents.rst into installation.rst
Change-Id: I897cfe0094358db63a364088fd2b977e234101e8
20ccb58e67