feature/api-controller-improvements (#567)

* added error handler for api controller
* while downloading the config from the api, the Connecting status is now displayed
* added a button to delete container config for api servers
* added crc check to avoid re-import of api configs
* fixed currentIndex of serversMenuContent after DefaultServerIndexChanged
* added closing the import window after re-importing the config from api

client/core/defs.h

@@ -88,7 +88,11 @@ namespace amnezia
         ImportInvalidConfigError = 900,
 
         // Android errors
-        AndroidError = 1000
+        AndroidError = 1000,
+
+        // Api errors
+        ApiConfigDownloadError = 1100,
+        ApiConfigAlreadyAdded = 1101
     };
 
 } // namespace amnezia