Revamp the inputMethodQuery for konsolepart.

1. Surrounding text does not make sense for terminal, because surrounding text is used by input method for text predication, usually used together with deleteSurroundingText (commitString with negative offset), which is impossible for terminal application because it requires directly modify the buffer. Return value for surrounding text may cause invalid expectation from input method, e.g. input method may wrongly treat the command prompt as a part of text in the text buffer.
2. Fallback inputMethodQuery to QWidget default implementation, this allows ImHint to use QWidget::inputMethodHints().
3. Set default input method hints that makes sense for terminal.