Form / Form Element: is_modified() returns whether content has been changed
Form Element Form/Array: Override is_modified()
Form Element JSON: override is_modified()
(JS) array_compare_values(): compare values of two arrays
Form Element Checkbox/Keywords: override is_modified()
Form Element *: show_element()/refresh(): use is_modified() to check for changes
(JS) Fix function array_compare_values() check for array not defined
Form Element JSON: Bugfix, input may contain no value -> return null
README: add example code
Instead of reset() call save_data()
Form Element File: handle single file upload
Form Element File: Provide a naming template for uploaded files
Form Element Directory: Upload multiple files to a directory