Make unity progress and counter themable

[Ypetremann]

I think that in dockbarx, theming take an important place, so what about make themable counter and progress that depend of the theme ( for example shinybar, that copy the microsoft bar, will have a green bar in the background ... )

For the progress we can make the size of a block to change, this filled with a reapeted image, mask an image with the block if we don't wan't a pure rectangular block but an image, the offset that depend of the progress, and finaly a if statement for the progress.

Dockbarx could be more awesome than unity ...