Boot sequence (#946)

* refactor bootsequence

* inf can be null

* align elements

libs/ev3/startup.ts

@@ -2,9 +2,5 @@
 console.addListener(function(priority: ConsolePriority, msg: string) {
     control.dmesg(msg.substr(0, msg.length - 1))
 })
-// pulse green, play startup sound, turn off light
-brick.setStatusLight(StatusLight.GreenPulse);
-// We pause for 100ms to give time to read sensor values, so they work in on_start block
-pause(400)
-// and we're ready
-brick.setStatusLight(StatusLight.Off);
+// boot sequence
+brick.showBoot();