Previously, if no themes were active, the gutter colors would
not be set. This would, effectively, give you random gutter colors
on TextMate startup. (or, sometimes, a completely transparent gutter).
Previously all the colors were calculated so setting e.g. the icon color made it sort of necessary to also set the iconHover and iconPressed color.
Now the default icon hover and pressed colors are a potential user supplied icon color. Likewise, the default icon color is a potential user supplied foreground color, etc.
This removes all the blending, the need to provide a scope selector to obtain them, and no longer taxes the general syntax highlight (by no longer having to carry around a dozen gutter styles per scope).
Use the text foreground color for icons when the theme doesn’t provide a color and introduce ‘gutterSelectionIcons’ for the color of selected icons (defaults to selected foreground color).
Also changed the gutter selection border color to match the divider color (when it isn’t specified by the theme).
Previously if the color for X (where X is e.g. foreground or invisibles) had an alpha value other than 1.0 (fully opaque) it would be blended against the less specifically scoped color for X rather than the background.
There was no real logic behind the previous design other than to treat all color blending the same and it would cause a problem for 1.x themes using transparency for selection or invisible characters.
Closes issue #285.
