Invalid designs from other mods should not be loaded from the library

[ekolis]

Describe the bug If you make a design in one mod using components from that mod, then play a game in another mod, designs from the first mod appear in your library but they're missing the invalid components. Instead, the designs just shouldn't appear at all.

[ekolis]

However not loading them from the library does not mean they should be removed from the library when saving the library at the end of a player session. They need to be preserved somehow.

• Saving off raw serialized text?
• Separate libraries for each mod (boo)?
• Something else?

[ekolis]

I think we need the concept of a reference to an object that doesn't actually exist, but the reference itself can still exist.