Change Sprite-String to reference in UserVariablesContainer, Remove warnings
Merge branch 'master' into XMLChanges
refactor xstream aliases

* spriteList -> objectList
* userVariables -> variables (container for variable lists)
* projectVariables -> programVariableList
* spriteVariables -> objectVariableList
xstream alias refactoring

* change in naming of members; sprite->object (for references)
* pointedSprite -> pointedObject
increase catrobatLanguageVersion to 0.6
add xmlheader entry for tags
Merge pull request #204 from Catrobat/XMLChanges

xml version 0.6