Issue 208 shareroom password conveyance

1. Make PubSharesPassManager refer to accountModel for the current account
   info, rather than relying on being called at login for it.  (There may
   not be a login, if resuming an old session by deserializing the
   accountModel.)
2. Correct the keys under which PubSharesPassManager indexes the passwords,
   using bo than {"shareId": shareId, "roomKey": roomKey}, rather than
   (whoops) {"shareId": roomKey}.
3. PasswordProtectedCollectionBase derivatives don't ever have share_id or
   room_key, remove the superfluous code.