Fix projects wrongly created with default theme

Projects that should have been created with the Jamaican Psalms theme
were getting the default theme instead, because the ProjectModel
constructor wasn't actually using the domainToProjectCode function that
had been written for the purpose. This was causing problems when running
certain E2E tests, and would have been causing problems for the real
Jamaican Psalms site as well if anyone had been creating new projects on
that site. Chalk one up for E2E testing doing its job.