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

@howbazaar @davecheney should these be names.EnvironTag and names.UserTag or are they ok to be stored as strings here?