Improve configuration templates flexibility

Configuration templates content needs:

• factorization (too much duplicated resources)
• conditional inclusions

For instance, there are few changes in default-repository-config.xml depending on the database. In the same file, there are options specific to the binary storage.
Having the database type used in the templates list is a consequence of the current non-flexibility, it would be nice to get rid of that.

There seems to be two solutions:

• using a template engine such as Freemarker
• introduce "fragments": replacing a parameter with a block containing parameters, the block being called a "fragment" and its name being parameterized.

Being compliant with previously existing custom templates would be better.