Request internet permission before connect for iOS (#794)

* Attempt to fix API error 1100
* NSURLSession fake call to exec iOS network settings dialog
* use http://captive.apple.com/generate_204 for requesting internet
permission
* moved MobileUtils to IosController
* replaced callbacks with signal-slots in apiController

client/core/defs.h

@@ -99,6 +99,9 @@ namespace amnezia
         // Api errors
         ApiConfigDownloadError = 1100,
         ApiConfigAlreadyAdded = 1101,
+        ApiConfigEmptyError = 1102,
+        ApiConfigTimeoutError = 1103,
+        ApiConfigSslError = 1104,
 
         // QFile errors
         OpenError = 1200,