Email install hook on more specific action

The original action "init" was even called on frontend pages. This action name was the most specific I could come up with.

Also I've found two identical functions: `jigoshop_upgrade_1_13_3` and `jigoshop_create_emails`.
I can see (and I was also complaining about this before, if you remember ;)) that these two serve different purposes, I'm just wondering if `jigoshop_upgrade_1_13_3` could just simply call `jigoshop_create_emails` and there would be no code duplication. Of course the duplicated code doesn't harm me in any way, I'm just sayin'...