Infer (class of (parameters of (functions defined in instances)))

Example:
````arend
\class B
| v : Nat

\class C
| f (x : B) : B

\instance inst : C
| f x => \new B {
| v => suc (x.v) -- but currently we have to write (B.v {x})
}
````
This might be related to #126.

Start with the Arend example in the issue and compare the required explicit `(B.v {x})` form with the desired `x.v` shorthand. Trace the implementation of parameter and class inference, then verify that the example works when the shorthand is supported.

Written by the indexing model from the issue text.