Sample code for folding/unfolding and custom draw of attributes in Qt QTextEdit framework

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Only meant as example code to complete my answer to my question on StackOverflow: see http://stackoverflow.com/questions/19232882/nice-text-formatting-in-qtextedit-like-qtcreator-does

CapelliC @2015 (see http://stackoverflow.com/users/874024/capellic)