Starting on switching to, killing buffers.
CSS stylings; better status/minibuffer layout.
Revamped focus handling.

I still need to work around the known JavaFX bug/limitation that focusing the
contents of a tab after it is selected doesn't work, but focus management
between the buffer and the minibuffer is now much more robust.
Minibuffer revamp; no more read stack.

We now have one active read and any further attempts to read are rejected.
Status can "stack" over an active read and when the status goes away we return
to the read, but otherwise you just do one thing at a time.

Emacs allows limited read stacking, but I've always found that confusing so I'm
not champing at the bit to recreate that functionality. We'll see...