Added validation before saving any tunnels

Signed-off-by: Eric Kuck <eric@bluelinelabs.com>

WireGuard/Extensions/String+Arrays.swift

@@ -0,0 +1,24 @@
+//
+//  String+Arrays.swift
+//  WireGuard
+//
+//  Created by Eric Kuck on 8/15/18.
+//  Copyright © 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All rights reserved.
+//
+
+import Foundation
+
+extension String {
+
+    static func commaSeparatedStringFrom(elements: [String]) -> String {
+        return elements.joined(separator: ",")
+    }
+
+    func commaSeparatedToArray() -> [String] {
+        return components(separatedBy: .whitespaces)
+            .joined()
+            .split(separator: ",")
+            .map(String.init)
+    }
+
+}

WireGuard/Extensions/String+Base64.swift

@@ -0,0 +1,18 @@
+//
+//  String+Base64.swift
+//  WireGuard
+//
+//  Created by Eric Kuck on 8/15/18.
+//  Copyright © 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All rights reserved.
+//
+
+import Foundation
+
+extension String {
+
+    func isBase64() -> Bool {
+        let base64Predicate = NSPredicate(format: "SELF MATCHES %@", "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$")
+        return base64Predicate.evaluate(with: self)
+    }
+
+}