AP_Scripting: added opendog lua demo

libraries/AP_Scripting/examples/opendog_demo.lua

@@ -0,0 +1,23 @@
+-- demo of waving paw of opendog
+--
+local flipflop = true
+
+pwm = { 1500, 1500, 2000,
+        1500, 1500, 1000,
+        1500, 1500, 1500,
+        1500, 1500, 1500 }
+
+local angle = 0.0
+
+function update()
+   local t = 0.001 * millis():tofloat()
+   local angle = math.sin(t) * 0.5
+   pwm[6] = math.floor(1500.0 + angle*500.0)
+   for i = 1, 12 do
+       SRV_Channels:set_output_pwm_chan_timeout(i-1, pwm[i], 1000)
+    end
+    return update, 200
+end
+
+gcs:send_text(0, "opendog demo starting")
+return update, 1000