Added large (600x600) transparent layer as base of robot, so that accessories can now extend beyond
the left and front sides of chassis.
In addition to extending VirtualBot, robot configuration classes now serve as the controller classes for the corresponding ".fxml" UI markup files. Using the fx:id attribute in the ".fxml" file and the @FXML annotation in the robot config class allows automatic access to UI components.
Robot config classes are now registered using a @BotConfig annotation, so no changes to the VirtualRobotController class are needed when a new robot configuration is added.
Minor additional change: in hopes of speeding up app startup, the search for @Autonomous and @TeleOp op mode annotations is now limited to the teamcode package (and sub-packages). So, OpMode classes must be placed in the teamcode package or its sub-packages.
Added a new robot configuration: Arm Bot. It is a mechanum bot with an extendable arm, with a grabber at the end.