Email formatting improvements

Ready to merge
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Fixes in this commit:
* Removed sysname from subject line (added to end of message body in case it's needed)
* Conditional formatting of "Event Type:" or "Event 1 Type" depending if there are multiple events in an email
* "ts_created" is now "Date & Time"
* Removed "full dictionary" listing
* Changed unsubscribe information as per Lynn's suggestion
* URL for "unsubscribe" is now set in `CFG.system.web_ui_url` and is sensibly formatted if that entry is not supplied
* Human-readable description (using existing event formatting function)