Use new loadModel method in AliasDialogModel.

Change-Id: I509e95f7f4f6de31a0a99611ae4fb24c69657a8e
Depends-On: 17cdb63df9dde46a0a4a4761e03ffb24ae8bac55
Reviewed-on: http://gerrit.dmdirc.com/3622
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>