materialize some of the locked units [bounty: 9 XTR]

[DreadKnight]

Should be able to materialize some of the under development units, they could have "secret" value for playable data field and the materialization button would actually allow creating them. This way we could have more progress going on with units, while hotseat (and eventually online multiplayer) could either focus on the more stable units or go for new ones too.

At some point this could be limited to the development version of the game only (master branch) in order to avoid issues.