Also, use explicit unfolding lemmas for auth_valid and auth_validN.
The `Arguments valid _ _ !_ /` hack did not really work when one
has to deal with the valid instance of the cmra, which underneath also
includes a `cmra_valid`. Declaring a similar Arguments for `cmra_valid`
is a bad idea, it will also end up unfold stuff for the exclusive and
option CMRA.

This fixes issue #46.

Proof was done by Hai & me

This fixes issue #44.

No longer `put box_own_prop γ P` in the invariant, it is persistent.

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

ProofMode intro patterns: accept _ as part of variable names

@robbertkrebbers beat this. ;)

See merge request !29