Refresh Italian localization 2/2
Created by: erciccione
Refreshed present Italian localization
- improved consistency
- fixe typos
- refresh of all the translated pages
- deleted repetitions
- improved fluence of the text
- fixed broken markdown in /it/building.md
This PR is split in two parts. The first part is in kovri-site (ref: monero-project/kovri-site#42)