New toolbar navigation

[Casey Link]

> I frankly have no idea about last.fm* but from the screenshots i saw, i assume
> those functions were provided by the track actions (which i accidently added
> all next to the slider in the first place)
>
> Ideally i'd attach those to the current track, resp. replace or use the
> prev/next labels.
>
> You can assist me in the forefront:
> the navigation used to be done by toolbuttonactions, right?
> Is more information about the prev/next track provided by last.fm (and others)
>
> Love/ban etc. are simple buttons as well, yesno?

Yes the are buttons.
No they are not simple.

The issue isn't last.fm buttons specifically. We have an abstract
system for registering and displaying actions for the current track,
this system is aptly named:  CurrentTrackActionsCapability

Anyone (script, service, applet) can create and register a new
CurrentTrackAction and specify the type of track it works with (local,
stream, etc) and the icon is displayed on the toolbar for easy access.
An example of this is the Last.fm Love/Ban actions, and the Bookmark
action for bookmarking positions in tracks.

The point is that any sort of toolbar must support these actions and
at least a reasonable number (3-5).

Casey