QtNfc should support multiple adapters connected to the same system

PCSCLite (and Windows) API supports multiple adapters connected to the same system. Qt API expects at most a single adapter. This makes it weird to support PCSCLite because different adapters can have different supported protocols and also detect different cards. They can also be connected or disconnected at any time.

It would also be useful to support multiple adapter providers at the same time, like say PCSC and NearD on Linux.

To me the current class QNearFieldManager looks like a class representing adapters, except for some reason it can be created without providing any adapter specific data. It would be good to have an actual manager class that could be used to provide list of adapters and handle connections and disconnections (named QNearFieldInterfaceManager?).