centered check for updates button

main/ui/src/main/resources/fxml/preferences_updates.fxml

@@ -4,6 +4,7 @@
 <?import javafx.scene.control.Button?>
 <?import javafx.scene.control.CheckBox?>
 <?import javafx.scene.control.ProgressIndicator?>
+<?import javafx.scene.layout.HBox?>
 <?import javafx.scene.layout.VBox?>
 <?import javafx.scene.text.Text?>
 <?import javafx.scene.text.TextFlow?>
@@ -17,11 +18,13 @@
 	<children>
 		<CheckBox fx:id="checkForUpdatesCheckbox" text="%preferences.updates.autoUpdateCheck"/>
 
-		<Button text="%preferences.updates.checkNowBtn" defaultButton="true" onAction="#checkNow" contentDisplay="${controller.checkForUpdatesButtonState}">
-			<graphic>
-				<ProgressIndicator progress="-1" prefWidth="12" prefHeight="12"/>
-			</graphic>
-		</Button>
+		<HBox alignment="CENTER">
+			<Button text="%preferences.updates.checkNowBtn" defaultButton="true" onAction="#checkNow" contentDisplay="${controller.checkForUpdatesButtonState}">
+				<graphic>
+					<ProgressIndicator progress="-1" prefWidth="12" prefHeight="12"/>
+				</graphic>
+			</Button>
+		</HBox>
 
 		<TextFlow styleClass="text-flow" visible="${controller.updateAvailable}" textAlignment="CENTER">
 			<Text text="TODO Update to version "/>