Add the EnvUser with tests. Create an Environment user during bootstrap

Added the EnvUser doc

Support for setting the last login time for the EnvUser

Added a factory for adding the envuser

Admin EnvUser gets added at bootstrap time

Removed a couple of attributes from the upgrade package that no longer needed to be there

@davecheney @fwereade it's unclear to me what values I should be putting in here. At the moment I'm copying fields as passed to the AddUser call below. CreatedBy I'm guessing should be AdminUser. Where should alias be coming from? And for displayname this is currently the same as for the AdminUser