New definitions of displayed and vertical universal elements

[maxsnew]

This is a big refactor of the displayed universal property stuff we have so far:

1. Redefines displayed right adjoint so we don't need RightAdjoint' anymore.
2. Defines the fiber category over an object, and vertical composition between morphisms in the fiber and displayed morphisms.
3. Defines displayed universalElement using IsoOver, which corresponds more directly to the natural thing in eliminators for free categories
4. Give a separate definition of vertical universal elements which uses Iso and vertical composition
5. Changed to a simpler definition of cartesianLift

The code is still a bit of a mess and I think we should do some name changing, but wanted to push so @hejohns and I can discuss

[maxsnew]

@hejohns this is ready

[hejohns]

The new definitions look good. Haven't tried using them yet.
Just had a question in the comments on this PR about why some seemingly automatically generated normalized proof terms are there, when they don't seem necessary.