Blender Git Loki

Action Editor UI Tweaks:

While animating, I realised that actually the 'only selected' and
'include hidden' DopeSheet filtering options are also useful in the
Action Editor, especially while tweaking the animation for some
characters, where you'd like to focus only on some of the character's
control (i.e. eyelid tweaks, hand tweaks, etc.).

The other DopeSheet filtering options aren't so relevant here, so I've
excluded them from this.