definitions: [Z2] Add Z2K5/short descriptions, an optional Z12/multi-lingual string

… and use it to provide original quick descriptions of the main core Z4/ZTypes for now. We'll definitely want to re-visit all of these once we've decided on the final language we're using for things (e.g. not 'ZTester'), but for now this should hopefully suffice.

Bug: T290522 Change-Id: Ibfef2c0c78a2c33b98bf55049a3c85c1d2361a6e