Use _ind and _rec for eliminators, close #517
oops, add Types/Nat
global unset elimination schemes
actually, we want Local Unset Elimination Schemes
define Empty_rect
elimination schemes for sig
Local Unset Elimination Schemes in Overture, with documentation
update STYLE to conform to the Types/ reorganization
Merge pull request #578 from mikeshulman/stylereorg

update STYLE to conform to the Types/ reorganization
missing Local in Bool
comments about Coq bug 3745
Merge pull request #577 from mikeshulman/indrec

Use _ind and _rec for eliminators, close #517
Some lemmas about commutative squares.

I thought these would be used in more places, but I only found one.
Use records, not typeclasses, for subuniverses and modalities
Generalize connectedness to modalities.  Some typeclass business needs work.
more connectedness