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/updater/openvpn.go

@@ -1,7 +1,6 @@
 package updater
 
 import (
-	"net"
 	"strings"
 )
 
@@ -15,18 +14,6 @@ func extractRemoteLinesFromOpenvpn(content []byte) (remoteLines []string) {
 	return remoteLines
 }
 
-func extractIPsFromRemoteLines(remoteLines []string) (ips []net.IP) {
-	for _, remoteLine := range remoteLines {
-		fields := strings.Fields(remoteLine)
-		ip := net.ParseIP(fields[1])
-		if ip == nil { // not an IP address
-			continue
-		}
-		ips = append(ips, ip)
-	}
-	return ips
-}
-
 func extractHostnamesFromRemoteLines(remoteLines []string) (hostnames []string) {
 	for _, remoteLine := range remoteLines {
 		fields := strings.Fields(remoteLine)