Register KNSCore::Entry under name "Entry" as a Q_GADGET to QML
By making it a Q_OBJECT the enums can get exposed to QML, without making it a QObject and thus breaking BIC.
As suggested in https://phabricator.kde.org/T15180#269147, the value is registered under the normal and not core URI, because it is generally useful for consumers.
Task: https://phabricator.kde.org/T15180 Relates to https://phabricator.kde.org/T15141
cc @ngraham