[ #13801 ] Code cleanup (1/2)

src/Account.cpp

src/Account.h

src/AccountList.cpp

src/AccountList.h

src/AudioCodecModel.cpp

src/AudioCodecModel.h

src/Call.cpp

src/Call.h

src/CallModel.cpp

src/CallModel.h

src/CallModel.hpp

src/ContactBackend.cpp

src/ContactBackend.h

src/CredentialModel.cpp

src/CredentialModel.h

src/HistoryModel.h

src/InstantMessagingModel.cpp

src/InstantMessagingModel.h

src/VideoCodecModel.cpp

src/VideoCodecModel.h