Generate contrast themes, needed by the preferences framework, using Stylus

Currently the preferences framework uses a set of contrast themes to for setting the contrast. These have been written by hand and requires copy and paste and search and replace to create new themes. It would be much simpler to create these with a CSS pre-processor (Stylus: http://learnboost.github.io/stylus/ ) and a build step. This would allow integrators and ourselves to generate new themes quickly and easily.

Prior to Infusion1.5 the Prefs Framework specific themes were generated by a build process only, in 1.5 they were committed to the repo as we moved to a new build system. We could bring this type of behaviour back if needed with the above process.