Fix warnings about deprecated string conversions in V4-debugservice.

Change-Id: I1b45876d2016fdcf1117c4f77b33c75f7d712657
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Polish up QQmlFileSelector

Incorporate beta feedback, and hide QQmlAbstractUrlInterceptor as the
implementation (instead of making that "the API").

Change-Id: Ib7b14afeb9205fb8a87ed16a6d38b1f468b2aaaa
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Revert ffaf39e9a7f11d4e2800b3b37160a2a952795614

Making it public right now seems a little premature, given all the work
happening on the engine now (and for 5.3). We'll be in a better position
to commit to it or not next release.

Change-Id: Ib7b14afeb9205fb8a87ed16a6d38b1f468b2bbbb
Reviewed-by: Lars Knoll <lars.knoll@digia.com>