Added a seed_many url
Similar to the former user_start, user_end, and user_goal, only now
more generic. Also now properly propagates the 'step' argument.
Patch by: Sverre Rabbelier
Factor out ensureUser and add Error class in seed_db
Also removed the seed_many stuff, this will be moved to a seperate
url with in a more generic approach.
Patch by: Sverre Rabbelier