Switched Offer form and submission to Promoter from Agent

* Key user roles switched
* Promoters create offers now
* Agents can accept, reject and counter offer
* Agents and Promoters can generate contracts from Accepted Offers
* A few more functions were added to various model files
* validation was removed from Promoter's submit_contract action, it
kept failing with no error assigned. I'll fix later.
Merge branch 'Switching-Offer-Form-view/submission-to-Promoter'