[#1962] Use ALSA plugin dsnoop in order to share capture device

sflphone-client-gnome/src/config/audioconf.c

...-client-gnome/src/dbus/configurationmanager-introspec.xml

sflphone-client-gnome/src/dbus/dbus.c

sflphone-client-gnome/src/dbus/dbus.h

sflphone-common/src/audio/alsa/alsalayer.cpp

sflphone-common/src/dbus/configurationmanager-introspec.xml

sflphone-common/src/dbus/configurationmanager.cpp

sflphone-common/src/dbus/configurationmanager.h

sflphone-common/src/eventthread.cpp

sflphone-common/src/global.h