Add the ability to do simple (de)serialisation cycle in the JS unit tests. (And change the PQ, Trainer and Researcher serialisation.)

To catch e.g. typos.

• Use the same structure in the ProductionQueue item (de)serialisation as in Trainer and Researcher.
• Also iterate over the serialisable attributes on deserialize, as proposed by @elexis (on IRC), for its symmetry.

Proposed by: @Stan
Differential revision: D4388