Method to create default new users

Three methods to create users default (empty db) admin user

# options from just env variables
# use alternate env variables (mongo,root_url, email)
# random
Merge branch 'master' of github.com:ongoworks/reaction-core
Default to not showing any childVariants

Issue #22 last commit caused an empty variants value to be passed, which didn't show any, because no variant was selected.  I modified to have a more reasonable default (none).  I'm not sure that the currentProduct is setting currentVariant correct.