Doc: fix markups, capitalization and add 2 REVIEWING advices

I've been reading our entire documentation to see where it could
be improved. It's guide good actually. While reading I've fixed
some typos, added some capitalization to project names, mostly
trivial stuff.

What's worth reviewing is the 2 paragraphs I added to the REVIEWING
guidelines.

Change-Id: I977de335119f4ff7b9aedcfbed31c264ed531ea8
9 files changed