Key index parameters

A lot of blueprints implementations take optional parameters when creating key indexes specifying if the indexes are unique or whatever. Currently there's no way for you to pass those options if you are creating the key index through Pacer. 

This patch first loads the Parameter java interface from blueprints into pacer. I also modified create_key_index to take an optional 'opts' hash that is supposed to take in the parameters to pass to the blueprints implementation, transforming it into a blueprints Parameter in the process.