Remove AccountID type and AccountNULL define

sflphone-common/src/account.cpp

sflphone-common/src/account.h

sflphone-common/src/accountcreator.cpp

sflphone-common/src/accountcreator.h

sflphone-common/src/audio/audiortp/AudioRtpFactory.cpp

sflphone-common/src/audio/audiortp/AudioRtpFactory.h

sflphone-common/src/dbus/callmanager.cpp

sflphone-common/src/iax/iaxaccount.cpp

sflphone-common/src/iax/iaxaccount.h

sflphone-common/src/iax/iaxvoiplink.cpp

sflphone-common/src/iax/iaxvoiplink.h

sflphone-common/src/managerimpl.cpp

sflphone-common/src/managerimpl.h

sflphone-common/src/managerimpl_registration.cpp

sflphone-common/src/sip/sipaccount.cpp

sflphone-common/src/sip/sipaccount.h

sflphone-common/src/sip/sipvoiplink.cpp

sflphone-common/src/sip/sipvoiplink.h

sflphone-common/src/voiplink.cpp

sflphone-common/src/voiplink.h