Minor refactor in events
Added command to add/remove entities from model
Updated Index to process new event type
Added new scene model action
Added method to add entity event listeners
Fixed missing entries from engine skin
Fix Undo/Redo enable notifications
Merge pull request #478 from manuel-freire/fix-missing-engine-skin-entries

Fixed missing entries from engine skin
Merge pull request #477 from anserran/undoredo

Fix Undo/Redo enable notifications
Minor improvement in Accessor to facilitate debugging
InitEntity schema
InitEntityProcessor added. It just produces an EffectsComponent.
EffectsComponents has been modified to support arguments. That may be useful not only for initialization, but for other cases. Also, it was the simplest and probably most efficient way of implementing entity initialization.
Adding support in EntitiesLoader for entity initialization
bindings and DefaultEngineInitializer (can be skipped)
Test added
Minor fix in ChangeEntityPropertyExecutor
InitEntity transformed to Script.
ScriptCall effect added
EffectsSystem modified to make special processing of ScriptCall, instead of using an ScriptCallExecutor. There was no way of getting this done with an executor, unless the executor received a pointer to the EffectsSystem for further iteration (take into account executor receives the Entity target, not the Entity owner)
Less relevant stuff (reverting EntitiesLoader and EffectsComponent, adapting test, etc.)
Minor fix in debug output produced by EffectsSystem