Merge request changes

- Moved certificate-related utilities to separate class

- Added settings method to return an entire SSLSettings object; refactored
  methods using separate parameters to take single SSLSettings parameter

- Advanced Settings section on login page now hides / shows along with
  other buttons to prevent it from showing up in front of the loading
  spinner

- Fixed star imports

- Refactored applySslSettings as per code from merge request

- Fixed formatting

app/src/main/java/com/github/gotify/service/WebSocketService.java

@@ -42,7 +42,9 @@ public class WebSocketService extends Service {
         super.onCreate();
         settings = new Settings(this);
         missingMessageUtil =
-                new MissedMessageUtil(ClientFactory.clientToken(settings.url(), settings.validateSSL(), settings.cert(), settings.token()));
+                new MissedMessageUtil(
+                        ClientFactory.clientToken(
+                                settings.url(), settings.sslSettings(), settings.token()));
         Log.i("Create " + getClass().getSimpleName());
     }
 
@@ -79,7 +81,7 @@ public class WebSocketService extends Service {
         }
 
         connection =
-                new WebSocketConnection(settings.url(), settings.validateSSL(), settings.cert(), settings.token())
+                new WebSocketConnection(settings.url(), settings.sslSettings(), settings.token())
                         .onOpen(this::onOpen)
                         .onClose(() -> foreground(getString(R.string.websocket_closed)))
                         .onBadRequest(this::onBadRequest)