Doc: add link to Scalability topic

Add the link to topics that describe UI development
with Qt Quick.

Change-Id: Ib44e61f480d6417cec230bf9122a36af4c260749
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
iOS: Clarify Xcode 5 requirement for developing with Qt for iOS

Change-Id: I3472fb011f9e669efe5b8b8a7b90bfb662063688
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I702087ea1a6b416da7f9011419de6a17ccfc00c3