add help for :remote config for Gephi Plugin

This idea came from reviewing the patch for TINKERPOP-1297. Currently :remote config with no arguments returns an unfriendly message "Invalid config arguments - check syntax". It might be more user-friendly if :remote config either returned the existing configuration settings or if it listed some help.

:remote config help could let the user know what parameters are available and how they can be configured. Or perhaps something similar to how :remote connect works when you leave out parameters would help lead the user down the path of getting the syntax right.

Although I approached this from a Gephi perspective, it seems that the config options help must be based on the remote type, whether it is tinkerpop.gephi vs tinkerpop.server vs tinkerpop.hadoop.