Feature/inform

This pull request adds a notification modal if the user trys to book a graduate job even if he is not allowed to. By increasing single_job_offers_requested, the user is allowed to book a single graduate job.
The employer should be forwarded to the job_offer page - but how can I check this when it's only passing those attributes? Or is it valid that a job_offer_mail-template will be rendered when creating the job offer?