added push notifier thread, currently a no-op

Hooked up everything that needs to notify on pushes. Note that
syncNewRemote does not notify. This is probably ok, and I'd need to thread
more state through to make it do so.

This is only set up to support a single push notification method; I didn't
use a NotificationBroadcaster. Partly because I don't yet know what info
about pushes needs to be communicated, so my data types are only
preliminary.

Assistant/Threads/PushNotifier.hs

@@ -0,0 +1,21 @@
+{- git-annex assistant push notification thread
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Assistant.Threads.PushNotifier where
+
+import Assistant.Common
+import Assistant.Pushes
+
+thisThread :: ThreadName
+thisThread = "PushNotifier"
+
+pushNotifierThread :: PushNotifier -> NamedThread
+pushNotifierThread pushnotifier = thread $ forever $ do
+	waitPush pushnotifier
+	-- TODO
+	where
+		thread = NamedThread thisThread