Improve predicate docs

[tyv]

Is there an existing issue for this?

• [X] Yes, I have searched the existing issues

The problem

Predicates are confusing. 
It seems like it should force AutoView to select that component no matter what, 
however, in fact it works like that:
The last component without predicate or the last one with predicate which returns true wins.

The idea is, when you add a component for the same type afterwards to give you option to narrow cases when it is used, so you can stay with general one by default.

Describe the solution you'd like

add relevant docs

Describe alternatives you've considered

No response

[tyv]

Also we should make sure that UISchema docs link presented