[doc] Expand tutorial list in tutorial.rst

We can order them properly in this way.
Move basic ros tutorial in beginner tutorial level
[doc] Add some tags for various tutorials
[doc] Fix some ink between tutorials
[testing] Fix fallout from ac05a50d

Hi Pierrick :)
[datastream] Provide a generic register_component for class based model

Avoids duplication in n-places.
Still possible to override for old fashion component or for specific
behaviour (see socket).
[pocolibs] Remove useless stuff from pocolibs_datastream
[doc] Rework a bit main tutorial pages

- Remove reference to build blender scene
- Add some introduction in all section
- Merge 'interacting with morse' in 'general workflow'
[doc] Update testing doc pages

- Remove reference to test_all
- Remove obsolete information about ROS
- Sync the example with real base_testing.py
- Teach about ctest
- Teach about how to run only one test

Fix #288
[builder] Allows alter to take kwargs in argument

It permits to pass properly configuration to modifiers
[doc] Mostly rewrite the user modifier documentation

- Rephrase the introduction
- Rewrite how to add a modifier to a component using Builder API
- Provide two examples, one without argument, and one with some
  arguments.

Fix #286
[doc] add rospy example. fixes #272
[examples] add Qt (PySide) VW example