Adding javadoc, some code cleanup, example drivers added
-added javadoc comments to Driver, ControllerModule, SensorModule (still incomplete)
-added doc/ folder to hold generated javadoc

Coordinator.java:
-API for sendCommand(), sendCommandAndWait(), and sendBinary() changed so that a reference to the calling driver is passed instead of a string name.

BlankControllerDriver.java, BlankSensorDriver.java:
-added two blank drivers to use as a base when creating new drivers.  These drivers are heavily commented, so it should be easy to follow along.