Add fonts into the build process

Changes to add font handling into the gruntfile and to the build scripts.

I have to say it's the first time working with grunt files for me, so whilst this works, I'm not 100% confident it's the right way to go about it.  I've mainly gone with a monkey-see monkey-do approach to the vendor_files.css logic.

I've also needed to change the main.less to expect the font to be in a different location - another option would clearly be to put the font in the location that it's expecting, but my gruntfile skills ran out of depth at about that point.