core: Fix code duplication in application::run()

No need to duplicate code for the specialized version of
application::run(). We can just call the more general one from it.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
include: Clean up osv/app.hh header

Clean up the osv/app.hh header file by reorganizing member definitions
and improving the API documentation.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>