Adds the ability to sync just one conversation

kordophoned/src/daemon/events.rs

@@ -12,6 +12,9 @@ pub enum Event {
     /// Asynchronous event for syncing all conversations with the server. 
     SyncAllConversations(Reply<()>),
 
+    /// Asynchronous event for syncing a single conversation with the server.
+    SyncConversation(String, Reply<()>),
+
     /// Returns all known conversations from the database.
     GetAllConversations(Reply<Vec<Conversation>>),