updated user preferences and application

UserPreferences/user_preferences_common.ts

@@ -0,0 +1,12 @@
+
+export var checkKey = function(key: string) : void {
+    if ("string" !== typeof key) {
+        throw new Error("key: '" + key + "' must be a string");
+    }    
+}
+
+export var ensureValidValue = function (value: any, valueType: string): void {
+    if (valueType !== typeof value) {
+        throw new Error("value: '" + value + "' must be a " + valueType);
+    }
+}