Absence of AllowUnqualifiedMatch on a qualifier disables defaults

[mdekstrand]

Right now, when @AllowUnqualifiedMatch is not specified on a qualifier, so fall-through is disabled, default annotations applied to the component interface are also disabled.

Is this the behavior we want? I am thinking not — that qualifiers should (by default) require explicit bindings, but allow fall-through to defaults.

@lhkbob?

[mdekstrand]

This is causing an issue in lenskit/lenskit#862.