AP_Scripting: added servo movement example script

libraries/AP_Scripting/examples/servo_scan.lua

@@ -0,0 +1,15 @@
+-- move a servo in a sinisoidal fashion
+
+local SERVO_FUNCTION = 94
+local PERIOD = 0.5
+
+function update() -- this is the loop which periodically runs
+  local t = 0.001 * millis():tofloat()
+  local pi = 3.1415
+  local output = math.sin(pi * t * PERIOD * 2.0)
+  local pwm = math.floor(1500 + 500 * output)
+  SRV_Channels:set_output_pwm(SERVO_FUNCTION, pwm)
+  return update, 20 -- reschedules the loop at 50Hz
+end
+
+return update() -- run immediately before starting to reschedule