Doc: update the Android tutorial

Use the Qt Quick Controls application wizard to
streamline the process.
Remove snippet files and store compilable example code
in doc/examples. Do not store generated files.

Change-Id: I920484e84b2ef23bce9e77a7b0eddf963fe94552
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>