A handful of bug fixes.

-- Line spacing was too big on the keycaps (I think it was picking up
the spacing from Bootstrap); fixed in CSS
-- DSA keys were showing the inner-border in the incorrect spot (wasn't
really noticable on the dark colors of Retro DSA); fixed in CSS
-- Replaced custom min/max functions with the correct Math.min, Math.max
functions.
-- The valiation for x/y offsets was too aggressive; for some
oddly-shaped keys, it didn't let you set values that were big enough.
-- Swapped the order of the keylabel tops for the primary & secondary
rectangles.  This ensures that the label is in the same place whether
stepped or not, at the expense of maybe affecting old layouts.