code: public static String setKeywordValue(String localeID, String keyword, String value) {
          LocaleIDParser parser = new LocaleIDParser(localeID);
          parser.setKeywordValue(keyword, value);
          return parser.getName();
      }
docs: Given a locale id, a keyword, and a value, return a new locale id with an updated
  keyword and value.  If the keyword is null, this removes all keywords from the locale id.
  Otherwise, if the value is null, this removes the value for this keyword from the
  locale id.  Otherwise, this adds/replaces the value for this keyword in the locale id.
  The keyword and value must not be empty.
  
  <p>Related: {@link #getBaseName(String)} returns the locale ID string with all keywords removed.
  
  @param localeID the locale id to modify
  @param keyword the keyword to add/remove, or null to remove all keywords.
  @param value the value to add/set, or null to remove this particular keyword.
  @return the updated locale id