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/init/InitializationActivity.java

@@ -116,7 +116,7 @@ public class InitializationActivity extends AppCompatActivity {
     private void requestVersion(
             final Callback.SuccessCallback<VersionInfo> callback,
             final Callback.ErrorCallback errorCallback) {
-        VersionApi versionApi = ClientFactory.versionApi(settings.url(), settings.validateSSL(), settings.cert());
+        VersionApi versionApi = ClientFactory.versionApi(settings.url(), settings.sslSettings());
         Api.withLogging(versionApi::getVersionAsync)
                 .handleInUIThread(this, callback, errorCallback);
     }