Doc: Improved example documentation

-added instructions on how to run the example
 (using \include to insert a section from qtbase/doc/global/)
-updated copyright year
-removed links to Qt 4 API
-rearranged some of the sections
-created links from the example pages to Qt Multimedia
-fixed QDoc warnings related to the example pages

Task-number: QTBUG-33597
Change-Id: Id45ce5cbd40dbfa384abd7260a316f6f6837c186
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>
Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>