Tests are now run using Python

Following some cleanup in WebKit, run-webkit-tests is now a python
script. Adjust our command line for this.
HaikuLauncher: set a path for local storage

Some websites (gist.github.com) enter a JS endless loop if this isn't
available.
Use C++11 override

This allows easier detection of WebKit API changes.
Some of our methods (mostly unimplemented ones) were deprecated, remove
them.