Add new actuator : PWM controller (#737)

* Initial generalization from a PWM LED controller, to a PWM controller.
Allow the config file to set the name of each channel and the number of channels.
Fade time is now per-channel, so MQTT messages can genuinely set an individual channel, and specify the fade time for that channel.
The default gamma is configurable in the config.

platformio.ini

@@ -202,6 +202,7 @@ build_flags =
   '-DZgatewayBT="BT"'
   '-DZactuatorONOFF="ONOFF"'
   '-DZactuatorFASTLED="FASTLED"'
+  '-DZactuatorPWM="PWM"'
   '-DZsensorINA226="INA226"'
   '-DZsensorHCSR501="HCSR501"'
   '-DZsensorADC="ADC"'
@@ -418,6 +419,7 @@ build_flags =
   '-DZgatewayPilight="Pilight"'
   '-DZactuatorONOFF="ONOFF"'
   '-DZactuatorFASTLED="FASTLED"'
+  ;'-DZactuatorPWM="PWM"'
   '-DZsensorINA226="INA226"'
   '-DZsensorHCSR501="HCSR501"'
   '-DZsensorHCSR04="HCSR04"'
@@ -693,6 +695,7 @@ build_flags =
   '-DZgatewayBT="BT"'
   '-DZactuatorONOFF="ONOFF"'
   '-DZactuatorFASTLED="FASTLED"'
+  '-DZactuatorPWM="PWM"'
   '-DZsensorINA226="INA226"'
   '-DZsensorHCSR501="HCSR501"'
   '-DZsensorADC="ADC"'