marking qrc as local scheme (avoiding "deprecated on insecure origins" warnings)

Trying to use navigator.geolocation.getCurrentPosition(), navigator.webkitGetUserMedia ... from qrc:/ URL prints a console warning

getCurrentPosition() and watchPosition() are deprecated on insecure origins, and support will be removed in the future. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.

We could avoid this warning by marking the 'qrc' scheme as either a local or secure scheme (see blink::WebSecurityPolicy, blink::SchemeRegistry).

Anyhow, marking them as local would restrict access to it from web pages, since "normal pages cannot link to or access URLs from this scheme". This might be a good thing to do in general, but might break existing applications.