[DS-1230] Aging tool to discover disused accounts

https://jira.duraspace.org/browse/DS-1230

Also includes a loader to recover last-login dates from log files.
Currently I get an AuthenticationException when I try to delete an EPerson.
Context.ignoreAuthentication() returns a boolean that indicates whether the authentication system is swiched off or not. This line should be changed to
    myContext.turnOffAuthenticationSystem();