Change templates shows too many templates #322
Description
When a customer tries to change the template of the site they are shown all available templates instead of just the templates supported by the plan they have purchased. When they choose a template that is not allowed the page appears to load forever but actually the ajax request finished with the error, you are not allowed to use this template, but it is not shown to the user. We should only show allowed templates on this page and we should improve the error handling so the user is shown any errors.