Doc: Update "Getting Started" guide for changes in Qt Creator 3.0

"Qt Gui Application" is renamed in Qt Creator 3.0. Outdated docs can
cause confusion for newcomers.

Task-number: QTBUG-35082
Change-Id: I2cf577f5686de945e764fc2ed0835fd916f6064e
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Doc: Fix version number


Change-Id: If8ecc3d917328a19cbf9d493f68d703ee70676fc
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Added platform notes for Qt Multimedia on Android.

Task-number: QTBUG-35075

Change-Id: I3840d048788321bef4fe655bef685af5b075d9ac
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>