doc: fix .rst files canonical heading order

The headings on some .rst files were not following the expected
heading order of using # for h1, * for h2, = for h3, and - for h4
This patch fixes that, and the doc/templates/*.tmpl files created
for folks to use as templates for creating board and sample docs.

Change-Id: I0263b005648558d5ea41a681ceaa4798c9594dd9
Signed-off-by: David B. Kinder <david.b.kinder@intel.com>