stratosphere/stratosphere — pull request #565 by fhueske (2014-03-13 08:47:20+00:00)
Title: Add support for group sorting to new Java API

Adds initial support for group sorting. Currently limited to:
- Reduce operator
- Tuple data types with field selector key definition

Also includes a fix for sorting of Tuples (multi field sorting and sort order #543) in ```TupleComparator``` and ```BasicTypeComparator```.