Evass

Reason for the error was my fault - inconsistency in REST API.

I fixed it, cleaned up a little, added a workflow proposal for the method handler.

Backed out the changed pr_gender_opts: this can't be changed (too many dependend use-cases, interop requirement to have "unknown" option), but it can of course be overridden in EVR.

Moved the AvailableShelters method into EVR (only needed there currently).

Added a bunch of @todos, though these are *suggestions*, not anyhow obligatory. Most of them are meant to allow re-use of the module in a wider context (NB there is someone urgently looking for exactly /this/ functionality - you're not developing a niche product here ;) ).