Add commands to update contact names on Signal servers

As Signal Desktop does not allow its users to update the contact names,
it would be nice to be able to update contact names from signal-cli when
the latter is the master device.

The command `setContactName` allow to set the name for the given contact
in the local store. `sendContacts` can then be used to push the updated
contact list on Signal servers.

Closes #228

src/main/java/org/asamk/signal/manager/Manager.java

@@ -1416,7 +1416,7 @@ public class Manager implements Signal {
         }
     }
 
-    private void sendContacts() throws IOException, UntrustedIdentityException {
+    public void sendContacts() throws IOException, UntrustedIdentityException {
         File contactsFile = IOUtils.createTempFile();
 
         try {