Name all subsystem reference consistently with an '_api' postfix and
clean up naming and folder structure in some cases.
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
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>