Use new app runtime functionality from webkit

With the new app runtime feature we can limit the access of running apps. Before every app
was able to access mostly every file via XMLHTTPRequest on the filesystem and is now
limited to a very few locations.

Signed-off-by: Simon Busch <morphis@gravedo.de>
Don't set app id as application name

The application name is used to determine the data storage location and as we only have
one web process running in the background we can't use another location for every app.
Depending on the startup order the location was always different and apps couldn't access
their cookies / offline storages reliable.

Signed-off-by: Simon Busch <morphis@gravedo.de>