use <enum>.values() instead of EnumSet.allOf()
Node uses null values and writes less to stream
udpate hyracks test cases to use null's
set coverage in split repeat to 1/2 the node's coverage
fix for null value in GraphStatistics
Merge pull request #57 from uci-cbcl/wbiesing/optimize-writes-in-genomix-data-using-nulls

optimize writes in genomix data using nulls