Updates to the cvlayers palette.

+/- buttons are now smaller
Layers label is not shown
Overall horizontal width of palette is smaller
Eyeball icon removed in favour of checkbox
 Horizontal compaction of palette enabled by the above eye->check change.

Note that if you have your own copy of the tango theme (not the one that is installed by make install) then you need to add the two lines to tango/resources to change from the eyeball icon in the palette.