Ignore malformed templates and template properties

This MR changes the fetching query of templates, such that each returned template is guaranteed to have a target class statement. Template nodes that do not have such a statement will be ignored. This is done because otherwise the service will fail to map the templates, making it impossible to fetch a range of templates, given a malformed template node exists. Furthermore, template properties that do not have a path statement or an order statement will be excluded from the template properties list for the same reason.