Quick addition of ButtonBoard docs

Nothing special (no recipes yet); just add the stuff necessary to the
reST to pull it from source and add it to the diagrams

Author: waveform80

docs/api_boards.rst

@@ -29,6 +29,13 @@ LEDBarGraph
     :inherited-members:
     :members:
 
+ButtonBoard
+===========
+
+.. autoclass:: ButtonBoard(\*pins, pull_up=True, bounce_time=None, hold_time=1, hold_repeat=False, \*\*named_pins)
+    :inherited-members:
+    :members:
+
 TrafficLights
 =============
 

docs/images/composed_devices.dot

@@ -12,6 +12,8 @@ digraph classes {
     LEDBarGraph->LED;
     LEDBarGraph->PWMLED;
 
+    ButtonBoard->Button;
+
     TrafficLightsBuzzer->TrafficLights;
     TrafficLightsBuzzer->Buzzer;
     TrafficLightsBuzzer->Button;

docs/images/composed_devices.pdf

@@ -35,4 +35,5 @@ digraph classes {
     Servo->CompositeDevice;
     AngularServo->Servo;
     Energenie->Device;
+    ButtonBoard->CompositeDevice;
 }