RecentUsageModel can list all aps and docs,
only aps or only docs. make possible to control that from QML
the api works, all existing code has the same behavior as before
generally makes sense
we have QQmlParserStatus in this class, we probably want to use it.
Can we pick something a bit more specific.
Everything fits under "usage"
refresh() implementation already has a check on m_completed (which is set on componentCompleted)