New EnvUser

Add:
 - the EnvUser doc
 - support for setting the last login time for the EnvUser
 - factory methods for adding the envuser

Create the Admin EnvUser at bootstrap time.
I think the intent here is to use the environ uuid that has been associated with the State struct.  The problem is that as of right now, this is only set during initialize.  I'm working on this bit of code at the moment in a few related branches.  We can probably ignore it for now.  But add a comment tag here to be worked out later.