first pass at using new keys

It compiles. It sorta works. Several subcommands are FIXME marked and
broken, because things that used to accept separate --backend and --key
params need to be changed to accept just a --key that encodes all the key
info, now that there is metadata in keys.

Types.hs

@@ -8,11 +8,9 @@
 module Types (
 	Annex,
 	Backend,
-	Key,
-	genKey,
-	backendName,
-	keyName
+	Key
 ) where
 
 import BackendTypes
 import Annex
+import Key