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.
We should check only for local users.  We should probably also check that the createdBy user exists too, however there is always the race condition as we are working across collections.  After we look, someone could remove them.