Feature/464 contact field

This pull requests solved #464 and #468 : An employer is now able to fill in his contact data in extra contact fields. By that the employer can be reached directly via email/phone or even mail. 
Furthermore there are now contact fields for each job offer which are pre-filled with the contact data of the employer.
Why do you create new job offers with copied attributes for the contacts here. You can just assign the job offers to a variable and then use this in the contact definition with `counterpart: job_offer`. If you do not want to link the job offers with the contacts however, you maybe should use different values for the attributes to make them distinguishable.