New operations for obtaining elements and the size of arrays, maps, etc.
New operations linked to operator factory
Test updated
Comments addressed
GameLayers => GameView
Merge pull request #536 from jtorrente/gamelayer-to-gameview

GameLayers => GameView
Back and forward icons changed
Updated icon if interactive zone
Merge pull request #537 from anserran/backnexticons

Back and forward icons were too similar to undo/redo
Merge pull request #530 from jtorrente/get&size_operators

Get & size operators for collections
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