- Corrected several \snippet paths and \example paths.
- Added missing example images.
- Marked several commands as code.
- Updated the exampledirs variable for qtqml.

Done-with: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Task-number: QTBUG-28898
Change-Id: I24aac17821f54de4bd5129c45b5bf96dc0f114b2
Reviewed-by: Liang Qi <liang.qi@digia.com>