Optimise Javascript when packaging the jsgui

On build:
* Use r.js/node to optimise and minify the contents of assets/js into
  a single file called gui.min.js.
* Replace the load of config.js in index.html with a load of gui.min.js

Means we go from seventy-odd requests to load javascript and templates
to two. Skip optimisation with -DskipOptimization flag.
Optimise CSS when packaging the jsgui

* Switch from linking stylesheets individually to including one that
  imports the others.
* The require.js optimiser appends all the imported stylesheets into
  one single large file
* The maven-replacer-plugin replaces the load of styles.css with one for
  styles.min.css when the project is packaged

Conflicts:
	usage/jsgui/pom.xml
Use minified version of require.js.