Allow retreving and updating group info and contact names via dbus (#62)

* dbus method to get contact info

* Add getGroupName method

* Save after updating contact name

* allow group updates over dbus

* Allow retreiving group member list as well

* Space after if before conditions if( -> if (

* Return an empty string if the contact is unknown

* Handle null/non-existant groups better

* Remove debug output and allow updating the avatar

* Remove extra variables in update messages