Started transitioning to Webkit 2.0

Unfortunately, webkit_web_view_load_string() is not implemented in the
2.0 API, so trying with load_html() for now. Seems not to work with SVG
images without tweaking.
Merge branch 'master' into webkit2
Add class private to AgApp
Copy the default chart CSS to the resource database
Load default chart CSS to AgApp’s private member, web_view_group

This will make sure at least one CSS is loaded for each web view created
later.
Remove WebKitWebView creation from Glade

The Glade template cannot assign an already created WebKitWebViewGroup
to the WebKitWebView it creates. Thus we need to create it manuallp
Merge pull request #31 from gergelypolonkai/webkit2

Move to WebKit2