MR Job configuration optimizations

Give single Reducers more RAM to prevent memory OOM Exceptions.
Set map ouptut compression codec to Snappy.
Increase Spill percentage to lower chance of spilling to disk.
Disable MEMTOMEM setting during reduce phase for the moment being.
also: now runs with smaller dataset (roughly 1%).
Map timeout & Counters implemented

GitPopulator has now a timeout which aborts long running map tasks.
A CounterModule now needs to be passed to the CCModule constructor.
Tests adjusted accordingly.
Added three counters in GitPopulator.
Extend HadoopPipelineTest to feature three mappers.

This is useful to actually exercise writing to
and reading from temporary tables.
Add more logging to HadoopPipeline.

Stuff is breaking, and I've no clue why. Adding some logging.