Restructured the guide to follow a basic three step process: Set up, develop,
build. All information that is independent of the OS selection was taken out of
of the OS related documents and placed in the general set up sections.
A new section, Developing Zephyr Applications, was added with links to all the
development relevant section of the documentation.
The content in local_development.rst was split between the setting_up.rst,
installation_linux.rst and installation_mac.rst files as appropriate.
This new structure provides a much better flow for developers beginning their
Zephyr develpment.
Applied all of Inaky's suggestions in the refactored content.
Minor markup fixes and language edits were also perfomed during the refactoring.
Fixed a cross-reference that was broken during the refactor.
Applied all the feedback from the first trial run.
Applied the feedback provided by David Kinder from TCS.
Change-Id: I3368a3a41ec9ad02cc4e7b37fe71c65abd8a7df9
Signed-off-by: Rodrigo Caballero <rodrigo.caballero.abraham@intel.com>