Endpoint: Always include pk

[micburks]

Don't allow users to exclude primary key column. This really screws up datum and the UI. You can't delete or update a row when the primary key is excluded. We should be able to exclude whatever columns we want and then the UI can always treat primary key separately, such as to hide it

row.fields().forEach(function(field) {
    if (!field.is_primary_key) {
        w.append(widget(...));
    }
});