After migrating to openstackdocstheme, there are several points
to be improved in the rendered HTML files.
* Cleanup unnecessary vertical lines for quote blocks.
Existing quote blocks are actually not intended and
leading extra spaces cause this.
This commit removes unnecessary leading spaces.
* Some quote blocks are converted into definition lists
to clean up vertical lines for quote blocks.
* Use code-block for better code highlighting.
* Specify maxdepth in user/index toctree.
Change-Id: I9add5a317718e97abce15b5ddbfa3d1208a01570
ff2ca65e5c