Polish the example.

- Point it to qt.io and add command line option handling
- Adapt size to screen for high resolution screens and to
  accommodate qt.io which does not work with small windows.
- Add Back/Forward buttons
- Load on editingFinished (return pressed) of address field.
- Handle errors in user input more gracefully by defaulting
  to about:blank

Change-Id: I4ed4efce16b1d4739ac9e413dbe6427b5367de1c
Reviewed-by: Christian Stromme <christian.stromme@digia.com>
Android: Remove dependency to Android Extras.

Use our private JNI API in Qt Core instead.

Change-Id: I4064a05601733e83f6db0ded0184390ba1910d73
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>