Issue: Make synonym automatic expiry optional when changing a pages name

So the current behavior is based on Google's guidance to maintain 301 redirects for at least 6 months to 1 year (varying based on who gave the guidance and when it was given) when content has changed locations. It seems that nowadays 1 year is the guidance, so the default behavior should, at the least, be made consistent with that. I have thought for a while that this should be made an option though, as it might take wiki maintainers by surprise if they weren't the ones to set the expiry.

Added a setting in VaultWiki: Content Types, "Default Expiration for Automatic Synonyms", in the next release. The default is 1 year. It can be changed to 0 to disable expiration (unless the editor manually sets an expiration).