More work on message fragmentation

Echo.java:
-uses new sendCommandAndWait() method to check echoed response

Coordinator.java:
-added getSensorList() and getControllerList() to get data about specific drivers

SensorModule.java:
-added static TYPE
-getSensorList() returns an ArrayList<String> now

ControllerModule.java:
-added static TYPE
-getControllerList() returns an ArrayList<String> now

echo.ino, led_flash.ino, basic_controller.ino
-removed all support for incoming message fragmentation
-mostly untested