Refactored GraphGenerator, added GroovySerialTests

* Made a Builder static inner class for GraphGenerator

* Added support for multiple edge labels to GraphGenerator

* Renamed about half of the methods in GraphGenerator, including some
  getters and the central graph generation method

* Added two traversal test cases to GroovySerialTest

* Fixed the vertex-centric index query test case in GroovySerialTest
  to use appropriate primary key values (this was incorrect in the
  last commit but sort of "worked by accident")

* Changed formatting, semicolons, def keyword usage, and visibility
  modified usage to make GroovySerialTest more Groovy-idiomatic
Increase GroovySerialTest vertices 1k -> 10k

Also doubled transaction count from 5 to 10.  More tuning needs to be
done to bring the tests up to several digits of precision -- tests
that only take a few tens or hundreds of milliseconds only have one or
two digits of precision.