doc: edit the Galileo Platform documentation

Edited for grammar, style, markup, linkage, consistency.
This change was resubmitted to avoid having a nickname as author.

Change-Id: Ie3a1a16c33939062ce2e139024afd2162a0c802d
Signed-off-by: Steve Ballard <stephen.r.ballard@intel.com>
Signed-off-by: Rodrigo Caballero <rodrigo.caballero.abraham@intel.com>