PARQUET-108: Parquet Memory Management in Java

PARQUET-108: Parquet Memory Management in Java.
When Parquet tries to write very large "row groups", it may causes tasks to run out of memory during dynamic partitions when a reducer may have many Parquet files open at a given time.

This patch implements a memory manager to control the total memory size used by writers and balance their memory usage, which ensures that we don't run out of memory due to writing too many row groups within a single JVM.
This is correct but we should push that up as much as possible. Also as it is a JVM wide problem we should be careful with making one just for parquet that assumes a portion of the memory is reserved for it. I know Pig has its own memory manager, what does Hive do to that regard?