Fix stratosphere pom.

The compiler plugin was configured under the wrong section. It used to
be a child of reporting but is now a child of build. Changing the source
and target properties in the old pom were without any effect.
Changes in the TupleGenerator:

    - For Tuple Fields:
        - start with index 0
        - are public (no getters and setters anymore)
        - can be accessed via f0,f1, etc. instead of a method T1(), T2(), etc.
        - setFields() allows for setting all fields at once
    - For CsvReader, ProjectOperator, TupleTypeInfo:
        - TupleGenerator generates code for classes which depend on the tuple arity.
        - A special String indicates where to put Tuple dependent code
Added integration test for Filter operator.