mmm-client-ui-widget: utilize bootstrap

[hohwille]

So far we have created our own CSS, layout, etc.
The hype around bootstrap and its responsive approaches is just to big to ignore. We can benefit from all the work of bootstrap by integrating it for our web implementations. This implies some odd styling instead of just class="Button" we need class="btn btn-default" but who cares :)

[hohwille]

https://github.com/paypal/bootstrap-accessibility-plugin