Privado support and bug fixes

Features

• Privado VPN support
• Optionally filter Windscribe by hostnames
• Update Windscribe servers information using their API

Bug fixes

• Gluetun can now reach other containers on its local Docker network
• Fix program build information writing at build time
• Fix bad json tag for PureVPN servers serialization

Code maintenance

• Remove PIA v3 servers support
• Small refactoring of HTTP control server code