Obtain PIA v4 server information from API (#257)

- Obtain CN for port forwarding https verification
- Obtain for each server if they support port forwarding
- Obtain for each server their IP address for openvpn UDP and openvpn TCP (one for each)
- Updater program updated to use API
- Hardcoded values updated for PIA v3 and v4 servers
- Clearer separation between pia v3 and v4
- Fixes #250

internal/constants/servers.go

@@ -21,13 +21,13 @@ func GetAllServers() (allServers models.AllServers) {
 			Servers:   NordvpnServers(),
 		},
 		Pia: models.PiaServers{
-			Version:   1,
-			Timestamp: 1599323261,
+			Version:   2,
+			Timestamp: 1602523433,
 			Servers:   PIAServers(),
 		},
-		PiaOld: models.PiaServers{
+		PiaOld: models.PiaOldServers{
 			Version:   1,
-			Timestamp: 1600458645,
+			Timestamp: 1602523433,
 			Servers:   PIAOldServers(),
 		},
 		Purevpn: models.PurevpnServers{