Once more: remove rest of deprecated messages getAccount, getInbox and getOutbox.

Addendum to commit ca29cff.
Merge pull request #440 from benma/remove_deprecated

Once more: remove rest of deprecated messages getAccount, getInbox and g...
Message/API rename: sendUserMessage -> sendNymMessage.
Message/API rename: getRequest -> getRequestNumber.
Message/API rename: deleteUserAccount -> deleteNym.
CREATE_USER_ACCT-> REGISTER_NYM.