doc: application: move build/run/debug docs after overview

This document's flow could be improved a bit. The overview section is
followed by somewhat dense reference material, which is then followed
by step-by-step instructions central to the application workflow.

Fix this up by moving the details to the end, and adjusting the
transitions between the sections a bit.

The diff looks like a mess, but this commit is mostly just moving
things around. There are also various grammar fixes incorporated from
review.

Reviewed-by: David Kinder <david.b.kinder@intel.com>
Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>

squash! doc: application: move build/run/debug docs after overview