ReplConsoleView multiline input + refactoring

Multiline input field in the ReplConsoleView. The UI elements have also been factored out into a trait. To evaluate code/change history, CTRL must be held as well.

CommandField keyboard events can now be overridden, too.
Adds missing super.dispose call
Cosmetics

Relax needlessly concrete members in Intermediate trait.
Merge pull request #515 from huitseeker/pr/489

ReplConsoleView multiline input + refactoring