Similarly deprecate Qt.application.inputPanel and
introduce replacement Qt.inputMethod.

Change-Id: Ie4fd467f93f75023c86b0a2d038d858fe5001146
Reviewed-by: Joona Petrell <joona.t.petrell@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: Sami Kananoja <sami.kananoja@nokia.com>