Added argument-hint code completion

Now we show a separate list with argument-hint items.

E.g. "function(|"
At | the "function" is added to the argument-hint list

There are still some issues, like:
-no declaration found for argument-hint items
-default parameters not supported yet
-the current parameter is not market out
-and probably other

But, they are not so important, and most of them can be fixed later on.

REVIEW: 125371