expose game.setScore in blocks

fix for https://github.com/Microsoft/pxt/issues/881

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

@@ -85,7 +85,7 @@
   "game.setLife": "Sets the current life value",
   "game.setLife|param|value": "TODO",
   "game.setScore": "Sets the current score value",
-  "game.setScore|param|value": "TODO",
+  "game.setScore|param|value": "new score value.",
   "game.showScore": "Displays the score on the screen.",
   "game.startCountdown": "Starts a game countdown timer",
   "game.startCountdown|param|ms": "countdown duration in milliseconds, eg: 10000",

libs/core/_locales/core-strings.json

@@ -110,6 +110,7 @@
   "game.createSprite|block": "create sprite at|x: %x|y: %y",
   "game.gameOver|block": "game over",
   "game.score|block": "score",
+  "game.setScore|block": "set score %points",
   "game.startCountdown|block": "start countdown|(ms) %duration",
   "game|block": "game",
   "images.createBigImage|block": "create big image",