JSON profile documentation updated to reflect SCDB and template library support

This PR is connected to recent SCDB template library changes to offer a native, integrated support for JSON profile. This simplifies the original documentation (that has been very instrumental to add the support, thanks!).

This may require a few additions on Aquilon...

I refer to non existing versions of Quattor as the template-library-core changes have not been released yet. I was suggesting the same approach as for 13.1.3: not a real release, just a template-library-core new tag.