manual/maintenance: updates for redesignations/merges etc

[yakra]

I don't believe (without looking) this is codified in the manual, but:
When a route is deleted due to being renumbered/renamed/redesigated as, or merged into, another route,
There's a longstanding practice among some of us to, rather than leave the root field blank, use the new route's root. (Often, this new route will have the old route as an AltRouteName.)
For example,
2019-10-12;(USA) New York;I-895;ny.ny895;Renamed NY 895.

Could maybe codify this in the manual & encourage people to do it more.
Maybe make it optional? Required?
Worth some discussion in the forum before going ahead with a manual change. If nothing else, having the discussion could make more people aware the option's available.