- added gool.ast.construct.CompoundAssign for += like statements
    * added gool.recognizer.java.JavaRacognizer.visitCompoundAssignment(CompoundAssignmentTree n, Context context)
    * added gool.generator.common.CodeGenerator.getCode(CompoundAssign compoundAssign) (and overides)
- trimed textuals operators in JavaRecognizer: no more extra spaces produced around operators