Fix locale usage in RSyntaxTextArea

Our code uses the locale explicitly for i18n. But RSyntaxTextArea uses
the default locale everywhere for its controls and dialogs. To combat
that we will just change the default locale at the start of the app.

Author: Eswcvlad

src/main/java/com/itextpdf/rups/Rups.java

@@ -62,6 +62,7 @@ This file is part of the iText (R) project.
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
+import java.util.Locale;
 import java.util.Properties;
 import javax.swing.JFrame;
 import javax.swing.SwingUtilities;
@@ -94,6 +95,13 @@ public static void showBriefMessage(String message) {
      */
     public static void startNewApplication(final List<File> files) {
         SwingUtilities.invokeLater(() -> {
+            /*
+             * While we get the locale explicitly for our localized strings,
+             * some of the 3rd party Swings components use the default locale
+             * for string (ex. RSyntaxTextArea). So we need to change the
+             * default locale for everything to look consistent.
+             */
+            Locale.setDefault(RupsConfiguration.INSTANCE.getUserLocale());
             setLookandFeel();
             final IRupsController rupsController = initApplication(new JFrame());
             setOpenFileHandler(