In order to isolate the implementation details of
HBASE-4676 (PrefixTrie encoding) and other DataBlockEncoders by putting them in modules, this pulls up the DataBlockEncoding related interfaces into hbase-common.
No tests are moved in this patch. The only notable change was trimming a few dependencies on HFileBlock which adds dependencies to much of the regionserver.
The test suite passes locally for me.
I tried to keep it as simple as possible... let me know if there are any concerns.