Removed some separators of perspective buttons; small bug fix
Notion of edition context added to model
Updated selectioncommand to set contexts
Updated set selection action.
Added set edition context action
scene listener uses setEditionContext action
AddSceneElement uses context as parent of the added entity
Edit scene updates the edition context
Merge pull request #538 from anserran/perspectivebuttonschanges

Removed some separators of perspective buttons; small bug fix
Move WalkComponent to components
Merge pull request #539 from anserran/contexts

Added notion of edition contexts
Merge pull request #544 from manuel-freire/move-walkcomponent

Move WalkComponent to components
Remove static reference in CommandTest