Unable to make attachment as zip file

I have created a quick patch which hardcodes the archive type as zip as I could work out how to pull the config option from Webform settings, but this will obviously need changing.

I also had to comment out the section which calls ```verifyArchive``` as this is expecting a tar file, not sure whether that whole chunk of code could be removed?

Attatched patch implements the default webform zip export as suggested.

Unless I'm mistaken this doesn't pull the config option from Webform settings, simply overrides for each export which is not ideal.