Add MIT license

This project is licensed under the MIT license.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add and integrate new loading spinner nas.js

After I have finished the early version of nas.js it has now been
integrated into this project. Thus, I got also rid again of spin.js.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>