Admin panel modify ToC/configuration

[AlexandreDubray]

I think it would be nice to have a "richer" interface for the modification of the configuration/ToC in the admin panel (especially for the configuration file which has a lot of things inside it).

For the ToC it might be something similar to the edition of the content (see #15 for the idea of hiding/deleting part of the syllabus,we would need to be linked between the ToC and the content).

For the configuration, I think that drop-down style sections with entries for each field + a little "help" or "what does this field actually do?" would be nice.