Fix query used to get template documents with associated document types

This is the query currently used:

SELECT * FROM Document WHERE tmpl:forcedTypes <> ''

But this query is incorrect because

• tmpl:forcedTypes is a multivalued property, so if at least one value is different (or null), it will match
• tmpl:forcedTypes default value is none, and not an empty string or a null value.

We should use the following query as the correct one

SELECT * FROM Document WHERE tmpl:forcedTypes/* <> 'none'

Note that the current query returns almost all documents, which could slow Nuxeo startup or raise errors and make the repository initialization fail.