Similar to what qtbase 1dbfbf4c66187e7522888c19d78024cfceaea570
did for QTextEdit. Now available only in plain text, html support
pending.

Change-Id: I0b23a45fc484512d3354f66e1a6134e2d70eb8b5
Reviewed-by: Andrew den Exter <andrew.den-exter@nokia.com>
Reviewed-by: Joona Petrell <joona.t.petrell@nokia.com>