Work on document structure and doc building

This patch clarifies the document structure of
doc/source/devref/development.environment.rst and adds a section about
how to build the documentation.  This patch also strips out the
redundant information in doc/README.rst, replacing it with a reference
to doc/source/devref/development.environment.rst.

Change-Id: Ia354dcbaea35b812327dac7371ea2fe9aec2b594
Closes-Bug: 1268424
Merge "Work on document structure and doc building"