Add boolean flag that artefact needs extended font-files or not

Pivotal: https://www.pivotaltracker.com/story/show/46101529

This adds a flag, `need_extended_font`, which defaults to `false`, that defines if an artefact requires the extended font. This is the first part of the work towards being able to load in the extended font file (the work @antimega has been doing) for artefacts that need it.