Minify viewer media

Those changes allows to embed image viewer on the static HTML website. All static files are minified using django-pipline and served on:
```
http://HOST/static/omeroweb.viewer.min.css
http://HOST/static/omeroweb.viewer.min.js
```
This PR should be tested using html static page in webtest/templates/webtest/embed. Double click on the file and see if you can view image in the viewer.