[doc] Fix several spelling issues in user/basic_morse.rst

While here, deal with a few other styles issue

This page must probably be updated to reflect last changes in morse
(environment, options restricted to certain commands, ...) (Hi
Séverin).
[builder] Fix missing call function in multinode case
[multinode] Update code to work with current core :)

- Get rid of self.gl which reference bge.logic and replace by call to
  blenderapi
  - self.gl.getCurrentScene() -> blenderapi.scene()
  - self.gl.robotDict -> blenderapi.persistent_storage().robotDict
- Adapt the call in main to create the different multinode handler
- fix a missing argument in base multinode class