Add a script to install Qt4 WebKit on Debian based distributions

On recent Debian, the package python-qt4.webkit has been deprecated and removed from official repositories. So, all Debian based distributions like Ubuntu 16.06+ will not serve this package anymore. It means that you will not be able to launch Drive because of lack of support of Qt4 WebKit bundles.

We will plan to upgrade to Qt5. In the mean time we can provide a script to do all the work to have a complete virtualenv with all needed libraries. It wil not pollute the system. Finally, the user will have to launch Drive from this virtualenv.

Note: it is a temporary fix for Drive developers/contributors and eventually for users using Debian based distributions with no more QtWebKit support. There will be a very limited support.