1) Added subsumption test to CacheVertex so that more restrictive queries can be answered from cache.
2) Renamed ImmutableLongObjectMap to RelationCache
3) Fixed ByteBufferUtilTest by using signum
Merge branch 'fix-for-performance' of github.com:thinkaurelius/titan into fix-for-performance
Rewriting of RelationCache to store properties of the relation directly (not in the map) and corresponding rewrite of EdgeSerializer where PropertiesHeader became redundant.