Simplify example code by using QmlApplicationEngine

Since QmlApplicationEngine does all the nasty bits
including setting the incubation controller, we should
use it in all of our examples.

Task-number: QTBUG-31203
Change-Id: Ie4f2313b66ef1a460aa50559f5c0a6125d0c69f1
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Text example: Update example.html

Remove references to QTextEdit and adapt it to match TextArea instead.

Update the Qt logo.

Change-Id: I6939bf7418fbad883e1d967bea3688d9ccfd4885
Reviewed-by: Hanne Linaae <hanne.linaae@digia.com>
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>