massive refactoring of how the environment is initialized and scripts are executed

- MongoContextFactory created and through MongoRuntime calls is initialized as global ContextFactory for Rhino
- ScriptableMongoObject created which all *.adaptor.* classes extend... this class extends ScriptableObject and overrides setParentScope() to set an internal reference to the parent MongoScope, throwing a MongoRuntimeException if the set parent is NOT a MongoScope instance
- MongoScope holds set of initialized com.mongodb.Mongo instances for cleanup via single method call
- MongoRuntime acts as a collection of convenience methods for creating MongoScope instances and executing scripts using the global MongoContextFactory
- JSTest refactored following changes