Revert "Merge pull request #554 from sharetribe/empty-messages"

This reverts commit 215247fe3a49842621a5032e0d3eef00b8bb0e68, reversing
changes made to bdf585352c465a352266831d699829514e078af6.
Remove mangopay columns from people
Remove mangopay models, views and referrals to those
Remove rest of Mangopay