doc: Add an improved application development section.

Introduces the first part Carol's original contribution. The original
contribution is broken up in multiple files. The updated toctree shows
the
files that will constitute the section. Edits for clarity,
redability and markup were also included. The old files were removed.

Change-Id: I29364c6bc94322c6235b51850c2d1b9f71eb1ad8
Signed-off-by: L.S. Cook <leonax.cook@intel.com>
Signed-off-by: Rodrigo Caballero <rodrigo.caballero.abraham@intel.com>