This is in preparation for coq/coq#9274.

In same spirit as the other 'primitive' types like `option`, `prod`, ...

It does not really help since the main work of the proof is in showing that
`cFunctor_map F (iProp_fold, iProp_unfold)` is injective, but whatever.

These unfolds kind of make sense, and I was quite surprised that
it used to work before. However, when changing to primitive
records, these unfolds are actually needed.

This way, it can be used with `iApply`.

This patch was created using

  find -name *.v | xargs -L 1 awk -i inplace '{from = 0} /^From/{ from = 1; ever_from = 1} { if (from == 0 && seen == 0 && ever_from == 1) { print "Set Default Proof Using \"Type*\"."; seen = 1 } }1 '

and some minor manual editing

    The idea on magic wand is to use it for curried lemmas and use ⊢ for uncurried lemmas.

The old choice for ★ was a arbitrary: the precedence of the ASCII asterisk *
was fixed at a wrong level in Coq, so we had to pick another symbol. The ★ was
a random choice from a unicode chart.

The new symbol ∗ (as proposed by David Swasey) corresponds better to
conventional practise and matches the symbol we use on paper.