Adds a deeper hierarchy to the Bluetooth Mesh documentation by moving
the modules in separate pages with a brief description of the concepts
in each module.
Adds the full list of specification defined Health model faults.
Signed-off-by: Trond Einar Snekvik <Trond.Einar.Snekvik@nordicsemi.no>
Move guides and APIs into separate directories and cleanup naming
introducing index files rather than named section files.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>