Ref T261, correct implementation of client provider

* made the interface a "real" interface and provided implementation as CCLientProvider
* aligned some function names with networl context
* network context "impl" also implements ICLientProvider

src/blackmisc/network/registermetadatanetwork.cpp

@@ -18,6 +18,7 @@ namespace BlackMisc
         {
             CAuthenticatedUser::registerMetadata();
             CClient::registerMetadata();
+            qDBusRegisterMetaType<CClient::Capability>();
             CClientList::registerMetadata();
             CEcosystem::registerMetadata();
             CEcosystemList::registerMetadata();