GraphSONInputForrmat now support modes, configurable via "faunus.graphson.mode"

Tested and worked for upgrading data from Titan 0.3.x to 0.4.x
using GraphSON extended via Faunus 0.3.x to generate output using "g._()"
and use Faunus 0.4.x to process the graphson generated by 0.3.x as the input.
(cherry picked from commit 8d2241f)