Created TupleBuilder for every Tuple, via TupleGenerator

Corr. Issue: https://github.com/stratosphere/stratosphere/issues/654

Made a TupleNBuilder for each TupleN class. 
All 22 builder get generated by the TupleGenerator.

The example from the issue can now be written like this:
```java
DataSet<Tuple2<String, Integer>> data = env.fromElements(new Tuple2Builder<String, Integer>()
	.add("hello", 1)
	.add("world", 2)
	.build());
```