Renamed static MemoryManager to MemoryManagerHelper
Renamed static MemoryManagerService to MemoryManager to make it clearer
Renamed static MemoryManagerServiceImpl to AllocatorMemoryManager to differ from new BufferMemoryManager
Merge remote-tracking branch 'github/buffer' into buffer
Moved AllocatorMemoryManager to allocator package
Moved UnsafeMemoryManager to unsafe package
Fixed compile errors due to exchange of MemoryBuffer to PartitionBuffer
Fixed PoolPartitionBuffer bug when reading from ByteBuffers