deprecate defaultString since it's now in the JDK (#51)

Author: elharo

src/main/java/org/apache/maven/shared/utils/StringUtils.java

@@ -1888,7 +1888,9 @@ public static boolean isNumeric( String str )
      * @param obj the Object to check
      * @return the passed in Object's toString, or blank if it was
      *         <code>null</code>
+     * @deprecated use {@code java.lang.Objects.toString()}
      */
+    @Deprecated
     @Nonnull public static String defaultString( Object obj )
     {
         return defaultString( obj, "" );
@@ -1904,7 +1906,9 @@ public static boolean isNumeric( String str )
      *                      <code>null</code>
      * @return the passed in string, or the default if it was
      *         <code>null</code>
+     * @deprecated use {@code java.lang.Objects.toString()}
      */
+    @Deprecated
     @Nonnull public static String defaultString( Object obj, @Nonnull String defaultString )
     {
         return ( obj == null ) ? defaultString : obj.toString();