more refactoring with new DSL module.
Add writeVertex OUT-only test.
refactoring mania -- ahhhhhhh.
Add kryo vertex reader test for IN edge read/write only.
Merge remote-tracking branch 'origin/master'
Add test for vertex writer for BOTH edges.
Test for writing vertex with BOTH in stream but requesting IN for kryo.
Test for reading vertex with BOTH in stream and OUT requested for kryo.
Get rid of weak failing assertion in generators.

Added todo for later improvement.
Check for exception if requesting BOTH when there's only OUT.
Test exception when requesting BOTH but stream only has IN for kryo serialization.
Test for exception where request IN/OUT but stream only has OUT/IN.
more tweaks to the refactoring of Traversal vs. GraphTraversal.