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.
Don't add steps in the middle, it just confuses the timeline.  Please move it to the end.  Especially as this means that when I land my branch that specifies the environ tag all the time on the *state.State object, you can change the state code to use it and not break the upgrade step.