This commit adds truncated 2-quotients, groupoid quotients, Eilenberg MacLane spaces, chain complexes, the long exact sequence of homotopy groups, the Freudenthal Suspension Theorem, Whitehead's principle, and the computation of homotopy groups of almost all spheres which are known in HoTT.
Add more theorems about mapping cylinders, fibers, truncated 2-quotient, truncated univalence, pre/postcomposition with an iso in a precategory.
renamings: equiv.refl -> equiv.rfl and equiv_eq <-> equiv_eq'
We move the basic notions of pointed types into init.pointed, to avoid cycles in the import graph. Also adds pointed versions of pi and sigma, with corresponding notation
Note: this is important. I proved a quite complicated equivalence with calc, by chaining these
equivalences. Now if I want to know the underlying function of this composite equivalence, I have to
unfold all these instances. Without the abstracts, this took 14 seconds, and afterwards, it took 2
seconds.
examples:
foo_eq : Pi {A B : foo}, _ -> A = B
foo_mk_eq : Pi _, foo.mk _ = foo.mk _ (if constructor is called "bar", then this becomes "bar_eq")
foo_eq_equiv : Pi {A B : foo}, (A = B) ≃ _
also changed priority of some instances of is_trunc
