Use multi-URL config params

Instead of deprecated single-URL params. Specifically, using these:
RemoteServerListURLs, ObfuscatedServerListRootURLs, UpgradeDownloadURLs

MobileLibrary/iOS/PsiphonTunnel/PsiphonTunnel/PsiphonTunnel.h

@@ -53,10 +53,10 @@ FOUNDATION_EXPORT const unsigned char PsiphonTunnelVersionString[];
  - `PropagationChannelId`
  - `SponsorId`
  - Remote server list functionality is not strictly required, but absence greatly undermines circumvention ability.
-   - `RemoteServerListUrl`
+   - `RemoteServerListURLs`
    - `RemoteServerListSignaturePublicKey`
  - Obfuscated server list functionality is also not strictly required, but aids circumvention ability.
-   - `ObfuscatedServerListRootURL`
+   - `ObfuscatedServerListRootURLs`
 
  Optional fields (if you don't need them, don't set them):
  - `DataStoreDirectory`: If not set, the library will use a sane location. Override if the client wants to restrict where operational data is kept. If overridden, the directory must already exist and be writable.
@@ -67,9 +67,9 @@ FOUNDATION_EXPORT const unsigned char PsiphonTunnelVersionString[];
  - `EgressRegion`
  - `EstablishTunnelTimeoutSeconds`
  - Should only be set if the Psiphon library is handling upgrade downloading (which it usually is _not_):
-   - `UpgradeDownloadUrl`
+   - `UpgradeDownloadURLs`
    - `UpgradeDownloadClientVersionHeader`
-   - `UpgradeDownloadFilename`
+   - `UpgradeDownloadFilename`: Will be set to a sane default if not supplied.
  - Only set if disabling timeouts (for very slow network connections):
    - `TunnelConnectTimeoutSeconds`
    - `TunnelPortForwardDialTimeoutSeconds`
@@ -83,7 +83,6 @@ FOUNDATION_EXPORT const unsigned char PsiphonTunnelVersionString[];
    - `LocalHttpProxyPort`
    - `LocalSocksProxyPort`
    - `TunnelWholeDevice`: For stats purposes, but must be accurate. Defaults to 0 (false).
-
  @endcode
 
  @note All other config fields must not be set.

MobileLibrary/iOS/PsiphonTunnel/PsiphonTunnel/PsiphonTunnel.m

@@ -234,9 +234,9 @@
         [self logMessage:[NSString stringWithFormat: @"RemoteServerListDownloadFilename overridden from '%@' to '%@'", defaultRemoteServerListFilename, config[@"RemoteServerListDownloadFilename"]]];
     }
     
-    // If RemoteServerListUrl and RemoteServerListSignaturePublicKey are absent,
-    // we'll just leave them out, but we'll log about it.
-    if (config[@"RemoteServerListUrl"] == nil ||
+    // If RemoteServerListUrl/RemoteServerListURLs and RemoteServerListSignaturePublicKey
+    // are absent, we'll just leave them out, but we'll log about it.
+    if ((config[@"RemoteServerListUrl"] == nil && config[@"RemoteServerListURLs"] == nil) ||
         config[@"RemoteServerListSignaturePublicKey"] == nil) {
         [self logMessage:@"Remote server list functionality will be disabled"];
     }
@@ -264,11 +264,29 @@
         [self logMessage:[NSString stringWithFormat: @"ObfuscatedServerListDownloadDirectory overridden from '%@' to '%@'", [defaultOSLDirectoryURL path], config[@"ObfuscatedServerListDownloadDirectory"]]];
     }
     
-    // If ObfuscatedServerListRootURL is absent, we'll leave it out, but log the absence.
-    if (config[@"ObfuscatedServerListRootURL"] == nil) {
+    // If ObfuscatedServerListRootURL/ObfuscatedServerListRootURLs is absent,
+    // we'll leave it out, but log the absence.
+    if (config[@"ObfuscatedServerListRootURL"] == nil && config[@"ObfuscatedServerListRootURLs"] == nil) {
         [self logMessage:@"Obfuscated server list functionality will be disabled"];
     }
 
+    //
+    // Upgrade Download Filename
+    //
+
+    NSString *defaultUpgradeDownloadFilename = [[libraryURL URLByAppendingPathComponent:@"upgrade_download_file" isDirectory:NO] path];
+    if (defaultUpgradeDownloadFilename == nil) {
+        [self logMessage:@"Unable to create defaultUpgradeDownloadFilename"];
+        return nil;
+    }
+
+    if (config[@"UpgradeDownloadFilename"] == nil) {
+        config[@"UpgradeDownloadFilename"] = defaultUpgradeDownloadFilename;
+    }
+    else {
+        [self logMessage:[NSString stringWithFormat: @"UpgradeDownloadFilename overridden from '%@' to '%@'", defaultUpgradeDownloadFilename, config[@"UpgradeDownloadFilename"]]];
+    }
+
     // Other optional fields not being altered. If not set, their defaults will be used:
     // * EstablishTunnelTimeoutSeconds
     // * TunnelWholeDevice
@@ -277,9 +295,8 @@
     // * UpstreamProxyUrl
     // * EmitDiagnosticNotices
     // * EgressRegion
-    // * UpgradeDownloadUrl
+    // * UpgradeDownloadUrl/UpgradeDownloadURLs
     // * UpgradeDownloadClientVersionHeader
-    // * UpgradeDownloadFilename
     // * timeout fields
     
     //

MobileLibrary/iOS/SampleApps/TunneledWebRequest/TunneledWebRequest/psiphon-config.json.stub

@@ -9,5 +9,7 @@ All other values will be provided to you by Psiphon Inc.
   "PropagationChannelId": "...",
   "SponsorId": "...",
   "RemoteServerListSignaturePublicKey": "...",
-  "RemoteServerListUrl": "..."
+  "RemoteServerListURLs": "[...]",
+  "ObfuscatedServerListRootURLs": "[...]",
+  "EmitDiagnosticNotices": true /* Useful when testing */
 }