made the widget movable

You can now move it to other bar.
An issue remain : when moved in new style mode the progress and image
texts are stuck. It works again if ff is restarted.
I also renamed a few ids/variables as to make more sense.
This is the only thing that is bothering me. You set the `title` attribute here, but the title is not displayed in the Customization view when ESB is moved to the unused toolbars/items. I'm not sure why is that.

Maybe we need a listener which will detect if ESB is moved into that area, so that it changes the look of ESB to something nicer?