Adden new icons
Added TweenPanel
New icons and strings
Minor change for use LinearLayout in tween edition
Changed the TweenButton
Refactored the MoreElementComponent.java
new strings
Added TweenEditionPanel to edit the tweens properties
removing getVariables() and copyGlobalsTo() from VarsContext. Seem unnecessary
Making Variables Poolable. This is necessary to prevent creating unnecessary Variable instances when multiple VarsContext may live together at the same time
Adding a VarsContext child to every VarsContext so a stack of VarsContext can actualy be implemented.
Also: VarsContext is now poolable
Adding support in VariablesSystem for having local contexts. See javadoc for a detailed description on how it works.
Fixing ConditionalSystem and ChangeVarExecutor after API changes in VariablesSystem
Fixing tests. Does not need to be reviewed
Test updated
Comments addressed
ConditionalSystem refactored:
- processEntity() method overriden to push a local context with the "$_this" variable that points to the entity that owns the condition. The code is sth as simple as:
```java
public void processEntity(Entity owner, float delta){
   variablesSystem.push().localOwnerVar(entity);
   doProcessEntity(entity, deltaTime);
   variablesSystem.pop();
}
public abstract void doProcessEntity(Entity entity, float deltaTime);
```
As a consequence, it was not necessary to pass Entity owner to the evaluateCondition method, which has been simplified
Fix all systems that depend on ConditionalSystem after latest changes in the api
"entity" reserved word replaced by "target". What do you think about it?
Minor fix after rebase.