complete uplaod when ask for promise
hate trailing conditions
dialog's arguments prepared in one place
common __onUploadComplete
more reliable cancel
undocumented method dimensions removed
validators implemented in files
move common parts from widget and multiple-widget to base-widget
do not call Dialog.addFiles on initialization and other fixes
forward validators from widget to files.
default validator for images-only
delay reloadInfo to next tick to allow add validators on page load