Merge branch 'groups-overhead'
file internals: __infoDf removed, more clear __uploadDf
removed this argument for all file's deferreds
rejecting uploadDf is always 'upload' reject
other rejects uses __rejectApi indirect
UrlFile refactored:
watchers now emit events instead of calling uploader callback
add bind_all to pusher mock
onSwitchedToMe is not necessary
collectsion.readOnly and files's wrappers are not necessary
validation
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
more validation cases
fix some error messages