CallFactory: add template methods, ID generation

src/account.h

src/call_factory.cpp

src/call_factory.h

src/conference.cpp

src/jamidht/jamiaccount.cpp

src/manager.cpp

src/manager.h

src/plugin/callservicesmanager.cpp

src/sip/sipaccount.cpp

src/sip/sipcall.cpp

src/sip/sipcall.h