Added categories to libraries

Fix #3812

Author: cmaglie

hardware/arduino/avr/libraries/SPI/library.properties

@@ -4,6 +4,7 @@ author=Arduino
 maintainer=Arduino <[email protected]>
 sentence=Enables the communication with devices that use the Serial Peripheral Interface (SPI) Bus. For all Arduino boards, BUT Arduino DUE. 
 paragraph=
+category=Communication
 url=http://www.arduino.cc/en/Reference/SPI
 architectures=avr