Don't build a new connection if it already exists

There was also a lot of unneeded overhead in Connection::new() to get
the path to compare against, so split that out into a settings struct

src/padfoot/connection/contacts.rs

@@ -25,7 +25,10 @@ impl telepathy::ConnectionInterfaceContacts for Connection {
     ) -> Result<HashMap<u32, HashMap<String, VarArgs>>, MethodErr> {
         println!(
             "Connection<{}>::get_contact_attributes({:?}, {:?}, {})",
-            self.id, handles, interfaces, hold
+            self.id(),
+            handles,
+            interfaces,
+            hold
         );
 
         let mut out = HashMap::<u32, HashMap<String, VarArgs>>::new();
@@ -73,13 +76,15 @@ impl telepathy::ConnectionInterfaceContacts for Connection {
     ) -> Result<(u32, HashMap<String, VarArgs>), MethodErr> {
         println!(
             "Connection<{}>::get_contact_by_id({}, {:?})",
-            self.id, identifier, interfaces
+            self.id(),
+            identifier,
+            interfaces
         );
         Err(MethodErr::no_arg()) // FIXME: should be NotImplemented?
     }
 
     fn contact_attribute_interfaces(&self) -> Result<Vec<String>, MethodErr> {
-        println!("Connection<{}>::contact_attribute_interfaces()", self.id);
+        println!("Connection<{}>::contact_attribute_interfaces()", self.id());
 
         Ok(vec![
             "org.freedesktop.Telepathy.Connection".to_string(),