Removed is_dry function from moisture sensors.

The water arduino will decide if the reading is dry or not. The sensor
arduino just takes a measurement and sends info over the wireless
connection.
Developed of the communication controller library.

Split the communication_controllers file into multiple ones.

Added a SerialController class which can output information to the
computer using the CommunicationController interface.

Modified the SIP.ino and sensor_arduino.cpp files to use the changes.