same fix than [1519fc4d], for transfer button this time

calls are added to history only after they are removed from the current calls list

general client cleanup / refactor
thread-safe clock updater thread stopping
fix double free on client exit

fix display of current codec
remove unused struct members

sflphone-common -> daemon
sflphone-client-gnome -> gnome
sflphone-client-kde -> kde
sflphone-plugins -> plugins

The SIP credentials are transmitted (between client and daemon) and
(un)serialized (in the config file) as a list of items holding:
    - realm
    - username
    - password

The password associated to the SIP account will be removed as it is
redundant with the first item of the list.
idem for the authentication username.