This can be used on handhelds where there is no browser.
The user does the login process on its desktop, saves the JSON in a file
and uploads it to its handheld through an unspecified mean and loads it
on ScummVM using this new button.
- remove Options widgets of the old wizard;
- add CloudConnectionWizard dialog;
- remove old widgets and add new ones in the layouts;
- update local webserver to allow passing a callback that needs to be called if storage was connected via /connect_cloud.
