Welcome is only interested in checking partitions, not
in resizing them, so stick to one library. This will
become moot when the checks move to partitionmanager
and KPMCore can do the things.
Use QNetworkAccessManager instead of raw QtDBus queries to
NetworkManager in RequirementsChecker::checkHasInternet(). This is much
simpler (i.e., less error-prone) and should be more portable (to, e.g.,
ConnMan).