Status bar improvements

[nwatson22]

• Adds the number of refuted nodes to the proof status bar.
• Adds a separator which separates the one line summary into 3 parts, one which is the proof status, one to do with structure, and one to do with status of the leaves.
• Changes the definition of branches to mean "how many Split and NDBranch targets are there?" instead of "how many Splits and NDBranches are there?" to more accurately reflect the degree of branching in a proof.

[PetarMax]

Great - could we please have a slightly different order, say:

pending-passed-failing-vacuous-refuted-stuck-terminal || (or some other separator) nodes-branches

Also, note that branches might not carry all of the information, since, for example, in minimised proofs I will likely have just one branching that goes many ways.