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.

I choose to edit the original article, keeping its date. If you think it is better, we can also rename the file to the current date and remove the old one. It's probably easier to access the history if we keep the same file name (and thus date).