Add macro for creating subcommand set in a way that is
accepted by C++ (SHELL_STATIC_SUBCMD_SET_CREATE). Currently,
it exists along with SHELL_CREATE_STATIC_SUBCMD_SET which is
used in the tree but it is not liked by cpp.
Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@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>