change frac_auth notation

See merge request iris/iris!259

The unbounded fractional authoritative camera

See merge request iris/iris!187

The unbounded fractional authoritative camera is a version of the fractional
authoritative camera that can be used with fractions `> 1`.

Most of the reasoning principles for this version of the fractional
authoritative cameras are the same as for the original version. There are two
difference:

- We get the additional rule that can be used to allocate a "surplus", i.e.
  if we have the authoritative element we can always increase its fraction
  and allocate a new fragment.

      ✓ (a ⋅ b) → ●U{p} a ~~> ●U{p + q} (a ⋅ b) ⋅ ◯U{q} b

- At the cost of that, we no longer have the `◯U{1} a` is an exclusive
  fragmental element (cf. `frac_auth_frag_validN_op_1_l`).

Add ghost data to locations

See merge request iris/iris!249

Fix regression with iSpecialize errors.

See merge request iris/iris!262

Fix error messages for iSplitL/iSplitR.

See merge request iris/iris!261

Alternative take on making proof mode terms more compact.

See merge request iris/iris!254