Fix EZP-21149: Fatal error when creating content type without "names" attribute

This PR resolves issue https://jira.ez.no/browse/EZP-21149

Input validation in `ContentTypeService::createContentType()`  is fixed.

Additional:

* improved input validation for `createContentType()` and `addFieldDefinition()` methods
* removed duplicated code in `LocationService`
* ContentTypeCreate identifier attribute marked as required
* various small fixes (typos and deprecated todos)