Fix typo. Improve consistency. Introduce different translations choices.

- Disambiguate Add/Insert which were both translated as Add.
- Change colloquial 'Ci sono dei problemi' with 'Sono stati riscontrati' to be more consistent with previous translation where 'riscontrati' where used.
- Dashboard acquires feminine gender in italian, change article to reflect this rule.
- Instead of 'indietro', use the more direct 'Torna' which means 'go back to'.
- Change 'ha' (has) with 'dispone di' (more commonly used for file/folder permissions) to be consistent with the rest of the translation.
- Change 'schema' with 'modello' http://dizionari.corriere.it/dizionario_inglese/Inglese/B/blueprint.shtml
- Change a passive action into an active one, as it sound more linear and direct.
- Change 'di profili' with 'dei profili' as the plural of 'del' is 'dei'.
- Change 'Gio' with more common 'Gi'.
- Change 'vi' (pretty formal) with 'ci' which is more friendly and inline with the style of the rest of the strings.
- Change 'URL' with 'Link' because int he text editor, link is more appropriate – URL sounds more technical and not comprehensive of the link text which is part of the outcome of the Link button.
- Get rid of the word 'sottopagina' where the original string does not use 'subpages'.