Move HDFS code to it's own subproject and get rid of HDFS dependencies in gemfire-core

Based on these discussions on the mailing list, we should remove the HDFS code from the core, as well has setCustomEvictionAttributes and EvictionCriteria from the public API:

http://mail-archives.apache.org/mod_mbox/incubator-geode-dev/201603.mbox/%3CCAFh%2B7k0bryRbXpCZKmk5PYn4GaqrYgE-wrEQoc36OO5NaAczvA%40mail.gmail.com%3E
http://mail-archives.apache.org/mod_mbox/incubator-geode-dev/201603.mbox/%3CCAFh%2B7k2mDmKPHCoWyTqOCR3RvZv8F0MLjQgdx_j3FNn8y5yAOg%40mail.gmail.com%3E

That code should added back on a feature branch. In addition the public API for HDFS which was removed as part of GEODE-429 will be added back to that feature branch. That's probably just a matter of reverting the commits listed in GEODE-429.