web-view: use web-context-class
web-context: all functions accept and return web-context-class
cookie-manager: implement cookie-manager-class
download: implement download-class
find-controller: implement find-controller-class
web-context: use download-class
web-context: use cookie-manager-class
web-context: use find-controller-class
web-view: implement WebKitLoadEvent enum via gobject