allow client to disconnect when handlers are done

added a waitgroup on websocketClient to keep track of handler
goroutines specific to the client
Serialize transaction creation.

Fixes #120.
Fix shutdown deadlock for ws notification queue.

While here, correct the comment on rpcServer.notificationQueue.

Closes #122.
Log an unexpected error that was encountered.

The stack trace did not make it evidant which request had caused this
issue, so add extra logging for the request that caused it.  Sanitize
this request if it may contain any secrets.

Additionally, in this situation, begin shutting down the wallet rather
than simply dropping the response.  This will help to catch the issue
since it's easier to notice all requests failing, rather than just one
that was dropped.  If shutdown takes an unreasonably long time, panic.
Fix logging for improper redeemingtx notifications.
Check websocket RPC auth for every method.

Previously, the createencryptedwallet and stop requests did not check
that the client had successfully authenticated to the server.  This
change moves the check outside of the select statement for these
special cased handlers (previously run from the default case) so an
auth check will occur even if a request method does not match either
of these two.
IMPORT PATH MODIFICATION CHANGESET
----------------------------------

Please use this changeset as the first one on top of the conformal codebase.
Note that if there are new imports, they need to be changed as part of this
changeset. In general, use "git rebase" on github.com/conformal's version
and apply this changeset first.
Task #396 on Task Board:

Create a stub websocket call getdepositscript.