AdBlock for the Active Webbrowser

- enabled by default, can be disabled in the config
- uses EasyList by default, additional providers can be added to the
config
- writes blackists to ~/.kde4/share/apps/active-web-browser/adblock
- Updates once a week by default (yes, config-controllable)
- Also plug a leak of NetworkManager

Code has been kindly borrowed from the Rekonq project and adapted to
work with the Active Webbrowser.

Merged from branch 'adblock'