Revert "Added wrappers for Hadoop functions"

This reverts commit 74dded1c2cb87c459be3444d1c7387bbc510e154.
[FLINK-1076] Extend Hadoop compatibility. Added wrappers for stand-alone Map, Reduce, and CombinableReduce functions.
[FLINK-1076] Return type determined via type extraction.
Added test cases.
Minor improvements and clean-ups.
[FLINK-1107] Hadoop Compatibility Layer documented

This closes #131
[FLINK-1076] Extended Hadoop Compatibility documentation to cover Hadoop functions