Ensure explicit options override spark conf options (even if the spark configuration includes specific usage configuration).

// Regardless of spark config the collection to use here should be "myCollection".
dfw.options("collection", "myCollection").save()

Support short form options: dfw.options("collection", "myCollection").save() Should be accepted rather than requiring dfw.options("spark.mongodb.collection", "myCollection").

Configuration errors should throw ConfigException rather than IllegalArgumentException or NumberFormatException.