doc: Edit the doxygen.rst file.

Minor changes to formatting to make guidelines clearer.
Edit for clarity, readability and markup. Cleared whitespace error.

Change-Id: I050857653303cfae32875b1b6c2151b22271c0b6
Signed-off-by: L.S. Cook <leonax.cook@intel.com>
Signed-off-by: Rodrigo Caballero <rodrigo.caballero.abraham@intel.com>