[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).
[bin] Export the whole sys.path in PYTHONPATH to Blender

The sys.path is not initialized in the same way with the python3
interpreter, and the inner python3 embedded in blender. So export fully
the sys.path through PYTHONPATH so the user get the expected environment
in blender context.

It was done before, but lost in 987162b787. Reported by Felix Ruess.
[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
[doc] Update syntax to call morse run for multinode scenario
[doc] Started a features matrix that compare MORSE with other simulators

Help is needed to complete it