xfconf data type quesions

[Nick Schermer]

First of all, I don't see why alpha is part of a color. But apart from
that, why not convert the color into a hex decimal string (like
gdk_color_to_string does). The # shows we're talking about a color
(well most people will recognize it that way) and strings like
#33335555ffff are easy to customize.

We could even add a convenient function in the library to save a
gdkcolor, since what we mostly use in Xfce/Gtk (gdkcolor -> convert ->
xfconf_channel_set_string and the other way around for parsing the
string to a gdkcolor with gdk_color_parse).

Nick