Create a new PersonaStore.
Create a new persona store to store the Personas for the contacts in s. 
            Passing a re-used source registry to the constructor (compared to the old Edsf.PersonaStore
             constructor) saves a lot of time and D-Bus round trips.
| r | the EDS source registry giving access to all EDS sources | 
| s | the EDS source being represented by the persona store | 
0.7.2