-better use of QDoc markup commands
-edited words and took out Qt 4 specific sentences
-edited for clarity of content and titles

Task-number: QTBUG-32765
Change-Id: I793023fa7c7c6b3a7d967aca74ca51dc7b03243e
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>