doc: extensions: application: Overhauld and add west support

Overhaul the application extension in order to modularize its structure
and add support for building, flashing and debugging with west.
Both west and CMake are now supported, even at the same time, in which
case instructions for both will be generated.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
1 file changed