Fix a typo in documentation

Task-number: QTBUG-33408
Change-Id: I84729139ff40ac62b29031eb161761a8205259cc
Reviewed-by: Mitch Curtis <mitch.curtis@digia.com>
Doc: split up Qdoc-manual

qdoc-manual.qdoc is now an overview document
Each section is a separate qdoc file
Title modification in minimal qdocconf qdoc file

Task-number: QTBUG-31801

Change-Id: I9e50eb8c4f1f501e9c0bc768372d4393b73053ed
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>