Add missing features

[marcoeilers]

• Quantified wands (see issue Missing a case for inhaling (quantified wand with predicates on both sides) #294 for the inhale; exhaling a quantified wand currently does not result in an error but is actually a no-op (!!!!), which is obviously incredibly unsound)
• Wands as triggers (maybe this is what Heap-dependent triggers not yet fully supported #257 is referring to?)
• perm for wands, forperm for wands and with more than one variable (issue Support new permission introspection features #243)

[marcoeilers]

• forperm is often incomplete, but this is due to triggering. I don't know what better triggers one could choose than { Mask[r, f] } and { Heap[r, f] }, so I don't think we can do anything about that.
• Resource triggers are also often incomplete. The trigger { x.f } is currently translated as { Heap[x, f] }, so it does not trigger at all on mask accesses. That seems bad to me and would be easy to fix.

[gauravpartha]

Thanks for the changes. I just added some minor comments, but looks good to me otherwise.

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