Allow reference by DaoFactory in foreign key definition

This PR extends @optilude great work and makes it possible to pass a DaoFactory to the references option of the foreign key definition:

      this.Author = this.sequelize.define('author', { firstName: Sequelize.STRING })
      this.Post   = this.sequelize.define('post', {
        title:    Sequelize.STRING,
        authorId: {
          type:          Sequelize.INTEGER,
          references:    this.Author,
          referencesKey: "id"
        }
      })