Servo library support (#1343)

* ateempt at bringin servos

* basic plumbing

* avoid math map duplicate

* missing parts annontation

* pretify parts

* extend appcompat layer

* updated strings

* more compat layer

* annotations

* don't rely on webmidi

* updated pxt ref

* bump pxt

* adding whenUsed

* updated v1 readme

* more pins

* more pins

* compress the parts definition

* update common packages

libs/servo/_locales/servo-jsdoc-strings.json

@@ -0,0 +1,5 @@
+{
+  "servos.Servo.run": "Set the throttle on a continuous servo",
+  "servos.Servo.run|param|speed": "the throttle of the motor from -100% to 100%",
+  "servos.Servo.setAngle": "set the servo angle"
+}

libs/servo/_locales/servo-strings.json

@@ -0,0 +1,10 @@
+{
+  "servos.P0|block": "servo P0",
+  "servos.P1|block": "servo P1",
+  "servos.P2|block": "servo P2",
+  "servos.Servo.run|block": "continuous %servo run at %speed=speedPicker \\%",
+  "servos.Servo.setAngle|block": "set %servo angle to %degrees=protractorPicker °",
+  "servos.Servo.setPulse|block": "set %servo pulse to %micros μs",
+  "{id:category}Servos": "Servos",
+  "{id:group}Servos": "Servos"
+}