When using the `allow-dependencies-licenses` option, the packages listed
there should be allowed even if they have no license. This wasn't
working because the filtering for allowed dependencies was done
specifically on the list of packages that had licenses, leaving a
separate list (unfiltered) for packages with no licenses. With this
change, we filter out any changes for packages that have been allowed
_before_ we retrieve licenses.

Fixes #889

The `allow-dependencies-licenses` option was not checking the namespace
part of the PURL to make sure it matched.

Allowing dependencies works with no licenses

The allow-licenses list is expected (and documented) to be a list of
SPDX license IDs (LicenseRefs are also valid). If someone puts an
expression in the list (e.g. "GPL-3.0-only OR MIT"), it should be
discarded so that the whole list does not become invalid.

Fixes #907

Discard allow list entries that are not SPDX IDs

Bump version number for 4.7.1