Add .xsjs and .xsjslib as JavaScript file extension

.xsjs and .xsjslib is used to denote server-side JavaScript files in SAP
HANA XS

samples/JavaScript/helloHanaMath.xsjslib

@@ -0,0 +1,9 @@
+/* simple hana xs demo library, which can be used by multiple endpoints */
+
+function multiply(x, y) {
+    return x * y;
+}
+
+function add(x, y) {
+    return x + y;
+}