Basic tasks (Mapper, Reducer and Combiner) for hadoopcompatibility

Wrappers for basic tasks (Mapper, Reducer, Combiner), new interface for OutputCollectors and a testcase with a complete Hadoop WordCount. With these in place, along with ```HadoopDataSource``` and ```HadoopDataSink``` the ground is set to start working seriously on the hadoop abstraction layer (which by the way is my Google Summer of code project and starts officially today :)) 

Notice that in some cases there is code that might be generalised  / refactored very soon.