Backport CMS7-6943 to 7.8 & 7.7: Dutch date format validation error in document editor displays wicket component id instead of field name

Steps to reproduce:

1. Start archetype
2. Select language "Nederlands" and log in as admin
2. Navigate to a news document
3. Edit news document
4. Remove date and enter invalid string, e.g. "1234"
5. Save document
6. An error message will be displayed "'1234' in veld 'date' moet een datum zijn".

(error message disappears very quickly, this is another known issue, see CMS7-4402).

The expected behaviour is, that the field name is used. Even better would be if the localized field caption would be used instead of the raw field name. But using the field name would already be an improvement.

(This document described how field captions can be localized: http://www.onehippo.org/7_8/library/concepts/editor-interface/add-internationalization-i18n-to-document-types.html)

Note that the English error message actually doesn't mention the field name at all. It just says "'1234' is not a valid Date".

The underlying issue is that this validation error originates in the underlying Wicket FormComponent. At this (lower) level there is no awareness of Hippo-specific configuration such as the template and field captions.