Added validations for member names:

2-25 chars long
alphanumeric and underscores only
disallowed: "growstuff", "admin", "moderator"

removed everything that was there to handle/truncate long usernames
since it's no longer needed.
make login names remember case (so I can have Skud)

... but don't let anyone take "skud" if I'm "Skud"

don't allow 'staff' as a login_name either
Merge branch 'restrict_usernames' into dev

* restrict_usernames:
  make login names remember case (so I can have Skud)
  Added validations for member names:

Conflicts:
	spec/factories/member.rb