presets.json - Let terms default to empty array

[westnordost]

I'd like to propose to default terms for a preset to an empty array if it is not specified. Currently there are 4520 presets without terms in the presets.min.json. Removing all these "terms":[] will reduce the presets.min.json by a bit.

[quincylvania]

@westnordost Sounds reasonable. Though we should also be better about adding terms to as many presets and fields as we can!

[westnordost]

Well, much stuff from NSI doesn't have terms

[bhousel]

Well, much stuff from NSI doesn't have terms

Thats ok, we should remove all of NSI, so it can be released as a separate preset pack.