CSS: bundle everything into one file

[TCL735]

Giraffe should provide one .css file that includes all CSS for all of its components.

There are consuming apps which may want to use a single .css file from their libraries in order to generate assets during their build processes. For example, the ui repository pulls in a single index.css for one of its other libraries (Clockface). By doing this, the ui repository is able put any assets that are included in the .css files into a folder for static assets during build time. Giraffe should do the same thing.

Doing this may have an impact on performance, so this request should also be considered from an performance standpoint.