Add sprintf.js v1.0.2.

This script provides sprintf() for JavaScript. It can be used for
example for translating strings used in JavaScript with variables.

It is licensed under BSD-3-Clause and can be found on GitHub:
https://github.com/alexei/sprintf.js

library/sprintf.js/src/angular-sprintf.js

@@ -0,0 +1,18 @@
+angular.
+    module("sprintf", []).
+    filter("sprintf", function() {
+        return function() {
+            return sprintf.apply(null, arguments)
+        }
+    }).
+    filter("fmt", ["$filter", function($filter) {
+        return $filter("sprintf")
+    }]).
+    filter("vsprintf", function() {
+        return function(format, argv) {
+            return vsprintf(format, argv)
+        }
+    }).
+    filter("vfmt", ["$filter", function($filter) {
+        return $filter("vsprintf")
+    }])