Timers (#235)

* adding timer support

* updates strings

libs/core/timer.ts

@@ -0,0 +1,51 @@
+namespace control {
+    //% fixedInstances
+    export class Timer {
+        start: number;
+
+        constructor() {
+            this.start = control.millis();
+        }
+
+        /**
+         * Gets the elapsed time in millis
+         */
+        //% blockId=timerMillis block="%timer|millis"
+        millis(): number {
+            return control.millis() - this.start;
+        }
+        
+        /**
+         * Gets the elapsed time in seconds
+         */
+        //% blockId=timerSeconds block="%timer|seconds"
+        seconds(): number {
+            return this.millis() / 1000;
+        }
+
+        /**
+         * Resets the timer
+         */
+        //% blockId=timerRest block="%timer|reset"
+        reset() {
+            this.start = control.millis();
+        }
+    }
+
+    //% whenUsed fixedInstance block="timer 1"
+    export const timer1 = new Timer();
+    //% whenUsed fixedInstance block="timer 2"
+    export const timer2 = new Timer();
+    //% whenUsed fixedInstance block="timer 3"
+    export const timer3 = new Timer();
+    //% whenUsed fixedInstance block="timer 4"
+    export const timer4 = new Timer();
+    //% whenUsed fixedInstance block="timer 5"
+    export const timer5 = new Timer();
+    //% whenUsed fixedInstance block="timer 6"
+    export const timer6 = new Timer();
+    //% whenUsed fixedInstance block="timer 7"
+    export const timer7 = new Timer();
+    //% whenUsed fixedInstance block="timer 8"
+    export const timer8 = new Timer();
+}