Add bootstrap framework to red

This adds the bootstrap framework to red. Currently no elements of the framework are used. 
bootstrap-red.css contains settings that override the bootstrap.min.css standard css. I tested with red basic, apw, pluto and blogbasic which should be basically unchanged currently by this change except for some slight changes in the headline markup.
Goal of this is to be able to use bootstrap UI-elements in order to offer a more consistent UI.