Top level module for font loading...
A FontLoader is an action from a list of fonts to a
FontLoadResult returned in
Fonts are supplied in a list of
Either FontDef FontFamily,
this is a little cumbersome but it allows the loader to load
individual fonts and / or a whole families with a single API
Tries to find the GhostScript metrics first...
Runs the IO action on the loader if it finds one.
Either of one of the environment variables
WUMPUS_GS_FONT_DIR must be defined
and point to their respective directory.