Replace the "Fraction" special by a string evaluation

Fractions are interpreted automagically, without the need to indicate a special.
This is thus a valid call:
    `echo "[1/3-0.1%]" | colout -l 0,1 "^\[.*%\]$" Scale`
Sort ressources before printing them
Adds default colormaps and update README

And bugfix: --debug in 256-colors mode