Little bit of this, little bit of that.

- Fixed `Menu` factory class and all of the items, nested items point are now classified in the right parent in the header.
- Page for Struttura created with a draft of a table and a search box.
- Added another function to the db.
- Doc updated.
- Added paging to `StrutturaResource`, `AttivitaResource`, `DipendenteResource`. `DipendenteResource` and `AttivitaResource` are broken, fix that.