@avigad and @fpvandoorn, I changed the metaclasses names. They
were not uniform:
- The plural was used in some cases (e.g., [coercions]).
- In other cases a cryptic name was used (e.g., [brs]).
Now, I tried to use the attribute name as the metaclass name whenever
possible. For example, we write
definition foo [coercion] ...
definition bla [forward] ...
and
open [coercion] nat
open [forward] nat
It is easier to remember and is uniform.
define embedding, (split) surjection, retraction, existential quantifier, 'or' connective
also add a whole bunch of theorems about these definitions
still has two sorry's which can be solved after #564 is closed
remove funext class,
remove a couple of sorry's,
add characterization of equality in trunctypes,
use Jeremy's format for headers everywhere in the HoTT library,
continue working on Yoneda embedding
also add more definitions in types.pi, types.path, algebra.precategory
the (pre)category library still needs cleanup
authors of this commit: @avigad, @javra, @fpvandoorn
