Add accept_job_offers field

This adds a field to the user profile, we can check to determine whether
the user wants to receive job offers by sponsors, see #78.
Fix #78 - Add ability to send job offers
Fix wording in translations
Further translation fixes
s/adminbox/sponsorshipbox
s/pagetitle/page_title
Don't redirect to success in JobOffer view
Add job offer template
Translate "Reply-To"
Add comment on mail connection
Always send people the the https version
Remain in JobView on success
Merge sponsorship job offer migrations
Add missing import
Make JobOffer.reply_to not nullable
Refers #78 -- minor changes
Merge branch 'job-offers' into develop
Update messages