Adding special variables that store viewport width and height
Adding layer for the camera. This way transformations applied to the camera don't interfere with scene transformations
Adding a scene component that stores a list of cameras. Each camera is defined as a "subrectangle" of the scene that can also have a rotation. Cameras are given an id so they can referred to in effects
Effect that changes the current camera. Please review calculus carefully - took a while to find out the tricky part described in javadoc
CoolDemo updated. Three new buttons demonstrate what we can do with cameras:
- Zoom into alien (animated)
- Zoom into chameleon + camera roll (animated)
- Zoom out (not animated)
Comments addressed
Merge pull request #627 from jtorrente/static-cameras

Static cameras
Variables and VariableDef moved to editor scope. Any reference to these classes in the engine has been removed
Minor improvements in EffectsSystem:
- Irrelevant entity argument removed
- Improved context management: unnecessary context created for each target has been removed
Support for registering variables with the set value
ScriptCallExecutor refactored
Added SetViewport effect. Needed for game initialization
GameLoader refactored
CoolDemo refactored and minor fix in test
GameData moved also from engine to editor
Save and Exporter updated to create behaviors component and effects for loading the game
Editor's engine also refactored
a couple of fixes after rebase
Fixed toolbars padding.
Changed games aspect ratio to 16:10.
Same aspect ratio as Nexus 10 screen.