[Feature Request] Allow cypher/trinket/artifact spells to be overwritten

[SnazzGass]

There should be a way to overwrite the spell part of a cypher/trinket/artifact.
Currently, you have to erase it, then throw some media, then create it with the new spell. Not only does this eat all the media in the item, but it also makes it an annoying process to reconfigure the spells in the items if you make a mistake.

It would be much nicer to just be able to replace the spell part (perhaps using scribe's gambit?) with a new spell. No random loss of media, no having to drop items on the ground to replace the spell.

In addition to making it easier to switch spells, this change would also allow cypher/trinket/artifact spells to overwrite themselves when #154 is fixed. You may worry that this change could make cyphers replace foci, but it's still not possible to read an iota out from a cypher/trinket/artifact, so you can't use them to store data.