Space object tags

**What do you want to see?**
Arbitrary player-assigned tags for space objects.

**How would it help players?**
Players could use these tags to filter their planets, ships, etc. And they could also be used for targeting scripted abilities, e.g. a long range cargo transporter.

**Alternatives**
???

**Screenshots and mockups**
N/A

**Things to consider**
Should these tags be limited to space objects, or should they be available to other game objects too?

Should players be allowed to tag objects that they don't own?

If players can't tag objects that they don't own, what happens to the tags when they lose ownership of those objects?

Should players be able to save their favorite tags to a library of some sort to reuse in other games?

If they can save them, should the library be global or per mod?

**Related issues**
N/A