Add user selectable Default Browser feature - part 6

- if a default Browser is not defined and if a Browser App
is selected into the disambiguation dialog, then make it as
the default Browser
- clear default Browser saved data (package name) when
the default Browser App is removed

See bug #20144393

Change-Id: Ia8621d7a61ec2cb60deded9d70f75f1e1d88d123