Sampling rate values are no more hardcoded. The sampling rate of the audio layer
 and the frame size can be set in the user config file. The clock rate of the codec we use
in the rtp session is set with his actual value, but can be changed by modifying
the available codec in the user config file (only G711 for now)

If an registered account is set by default, a call is placed with this account.
If no account is set by default, the call is made with the first registered account of the list
If a non-registered account is set as default, no call is placed and a message popup is thrown.

Conflicts:

	sflphone-gtk/src/calltree.c
	sflphone-gtk/src/menus.c
	sflphone-gtk/src/sliders.c