New PIA servers support (#227)

* Adapt storage: SyncServers write to file option, export FlushToFile
* CLI built-in updater for old and new PIA servers
* Update hardcoded IP addresses for PIA old and new servers
* Add PIA old to allServers struct and update timestamps
* Adapt code to work with new and old PIA servers
* Remove PIA subdomains (unneeded) from resolver tool

internal/updater/zip.go

@@ -0,0 +1,62 @@
+package updater
+
+import (
+	"archive/zip"
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/qdm12/golibs/network"
+)
+
+func fetchAndExtractFiles(urls ...string) (contents map[string][]byte, err error) {
+	client := network.NewClient(10 * time.Second)
+	contents = make(map[string][]byte)
+	for _, url := range urls {
+		zipBytes, status, err := client.GetContent(url)
+		if err != nil {
+			return nil, err
+		} else if status != http.StatusOK {
+			return nil, fmt.Errorf("Getting %s results in HTTP status code %d", url, status)
+		}
+		newContents, err := zipExtractAll(zipBytes)
+		if err != nil {
+			return nil, err
+		}
+		for fileName, content := range newContents {
+			contents[fileName] = content
+		}
+	}
+	return contents, nil
+}
+
+func zipExtractAll(zipBytes []byte) (contents map[string][]byte, err error) {
+	r, err := zip.NewReader(bytes.NewReader(zipBytes), int64(len(zipBytes)))
+	if err != nil {
+		return nil, err
+	}
+	contents = map[string][]byte{}
+	for _, zf := range r.File {
+		fileName := filepath.Base(zf.Name)
+		if !strings.HasSuffix(fileName, ".ovpn") {
+			continue
+		}
+		f, err := zf.Open()
+		if err != nil {
+			return nil, err
+		}
+		defer f.Close()
+		contents[fileName], err = ioutil.ReadAll(f)
+		if err != nil {
+			return nil, err
+		}
+		if err := f.Close(); err != nil {
+			return nil, err
+		}
+	}
+	return contents, nil
+}