fixes toString return value of min aggregation
Merge pull request #874 from vasia/fix_min_aggr_tostring

Fixes toString return value of MinAggregationFunction
Improved error handling when fetching optimized plan of programs.
Improve ConnectedComponentsExample with constantfields annotation
Aggregate Operator sets its semantic properties.
added murmurHash implementation
Minor cleanups for hash partitioner
Fixes an issue when generating a type erasure exception in TypeExtractor.
Functions can now implement ResultTypeQueryable to supply TypeInformation manually.
The Hadoop Compatibility has been refactored and extended to support the new Java API.
Hadoop compatibility now also supports MR2 API.
JobContext and TaskAttemptContext instatiation independent of Hadoop version.
Quick fix for successfully running the test case.
hadoopcompatibility: Wrappers and limit support for basic mapred hadoop tasks

* wrappers for Mapper, Reducer and Combiner (as a local Reducer) on the new Java API
* wrapper for  (OutputCollector)
* test case with an identity function.
* limitations present due type erasure issues and TypeExtractor
hadoopcompatibility: More explicit about null collector in HadoopOutputCollector
hadoopcompatibility: A full job runs, but with incorrect grouping. Test failing
hadoopcompatibility: Stronger type checking in wrappers
hadoopcompatibility: Iterator fix. WordCount works.
rebased
hadoopcompatibility: works!