Improve console REPL completion

[sxhya]

Improve REPL completion. Currently ImportCompleter will not work on this example:
\import Combinatorics.{-caret-}
Instead default completion will add Fin (instead of BinOp and Factorial).

Also make console completions smarter...

[ice1000]

This would be really really difficult as you may further want any projection terms to be completed

[sxhya]

I agree that it is difficult and unfeasible to implement REPL-completion with IDEA-plugin-like quality of output (at least for now) but in some simplest situations (e.g. the one that I've mentioned) it would be good to have completion working correctly.