Rearrange i18n Resource files into a directory

The "app/src/processing/app" directory became mess because there are
a lot of "Resources_*.po" and "Resources_*.properties" files for the
internationalization.

Moved the resource related files into a directory "i18n" under the
"app/src/processing/app" directory.

This is for developers only. No feature changed.

app/src/processing/app/I18n.java

@@ -35,7 +35,7 @@ public class I18n {
       if (language != null && language.trim().length() > 0) {
         Locale.setDefault(new Locale(language));
       }
-      i18n = ResourceBundle.getBundle("processing.app.Resources", Locale.getDefault());
+      i18n = ResourceBundle.getBundle("processing.app.i18n.Resources", Locale.getDefault());
 
       PROMPT_YES = _("Yes");
       PROMPT_NO = _("No");

app/src/processing/app/i18n/i18n_update.sh

@@ -18,7 +18,7 @@ trap "rm -f '$catalog' '$files'" 0 1 2 15
 
 # Generate the new text catalog without the already translated texts.
 # The 'merge existing' option for xgetext does not work propery for our purpose.
-find . -name '*.java' -print > "$files"
+find .. -name '*.java' -print > "$files"
 xgettext -L Java --from-code=utf-8 -k_ --output="$catalog" --files-from="$files"
 
 # Then, merge with already translated texts.