fix fall-back on custom font declaration

Both ways work in the end, but the fall-back happening here is not from one
font family to another but from a possible local installation of the same font
to using a webfont version from the app. The CSS handling this fall-back
should be the font-face declaration, not the family selector.
add SVG icons for new justification and hyphenation options
add toggle and styles for hyphenation and justification
change CSS to two letter language codes
convert hard coded lang values from ISO-639-2 to IANA
add utility to covert ISO-639-2 codes to IANA for hyphenation dictionaries
use new utility function to convert language codes just before they hit the html
fix text generator so html lang attributs use IANA codes