Make the Empathy core program act as a unique app.
Make the Empathy core program act as a unique app.

This means that instances beyond the first simply raise the initial instance and
exit.

Helps bgo#632912.

GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets