Create Xcode project, allowing easy editing of all sources.
the project uses "make mobile" and "make desktop" to generate the project,
so all CMake changes are automatically updated
the project uses folder references, so adding/removing a source is
automatically updated
The project expect build-mobile and build to be existing as well
as external libraries, so after cloning do a normal build before
using the project.
Signed-off-by: Jan Iversen <jani@apache.org>