Improve preference application performance on page load

Currently when loading a page that has preferences applied from the prefs framework, there is a slight delay between the page load and the application of the preferences. This may cause a flicker of the screen depending on browser caching, network latency, and speed of rendering and js/css interpretation. 

There may be a few ways to improve this:

• Provide an example/option for server side storing/application of preferences
  • e.g. apply theme classes as part of the server side rendering so that the correct theme is applied on load.
• Minimize CSS 
  • streamline CSS and/or lazy load so that not all of the options are loaded even when they are not used
    • see tools like PurifyCSS, PurgeCSS, uncss (see: FLUID-5915)