Added Font Sheets.

One can add a directory full of SVG files and get the Web fonts
for those. It works much in the same way sprite maps work, but
for fonts. It needs fontforge [http://fontforge.github.io/en-US/]

One should keep icons within a square viewBox. Each SVG will be scaled
to fit a 512x512 canvas with a baseline at 448.

autowidth trims horizontal white space from each glyph.
autohint adds hints for improved visibility under windows.
Sprite sheets didn't properly initialized sizes the first time