VZDump: added email notification setting

It's now possible to make VZDump only send a mail in case of a failure.

Signed-off-by: Tobias Doerffel <tobias.doerffel@ed-chemnitz.de>
VZDump: fixed typo in description for size parameter

Signed-off-by: Tobias Doerffel <tobias.doerffel@ed-chemnitz.de>
Fixed typo in backup API

Signed-off-by: Tobias Doerffel <tobias.doerffel@ed-chemnitz.de>
install missing file EmailNotificationSelector.js
bump version to 3.3-6