DRILL-336: Modified the netty direct memory manager to:
1) Efficiently reduce ("trim") the size of a memory buffer, releasing the extra memory back to the memory manager.
2) Opportunistically allocate larger buffers if it can be done efficiently.
3) Raise a warning exception if resizing a buffer copies more than 1 page of data.
4) Added Javadocs and some in-code comments.
5) Created a Junit test to verify basic functionality.
The "trim" and allocation changes are primarily in PoolChunkL,
which breaks a "chunk" into runs of pages using a buddy system.
Take advantage of memory interface changes.
Memory fixes
