Initial impl

This InputFormat allows decoupling the format of the data from the actual jobs. It implement isolation from classloader and configuration perspective.
It is intended as a better MultiInputFormat which allows reading a single input from multiple locations with different inputformats coming from separate isolated class loaders (child first class loading delegation) and configurations.

the goal is not to allow mapreduce inside mapred or vice-versa, just to wrap existing mapred or existing mapreduce, which may well be elephantbird bellow.