Refactor user_criteria into rules

• At the beginning of the process, I started to use Criteria as model name. Due to incompatibilities with MongoID for that work, I decided to move to UserCriteria. The problem is that at some point I thought that user was able to pick from a pull of Rules, instead of managing his own rules.

At the end User will be able to have a pull of rules from their own, that will be analyzed against companies uploaded by him, so I have renamed UserCriteria into Rule