Fixes for new Terasology serialization system (engine PR 3535)

[Cervator]

The new serialization system introduced by MovingBlocks/Terasology#3535 (tracking branch MovingBlocks/newSerialization) causes this module to no longer compile. 10 classes are affected and the changes seem fairly straight forward - although I'm not sure if any issues will result after.

Current users of Tasks include LightAndShadow (the NPC on the spawn platform - although I'm unsure if it still has an active quest?), ManualLabor (huh, no idea), and QuestExamples (has an example quest which is a task, so an easy test). The dependencies thus won't work either, but could be useful for testing when also fixed.

Sending this @eviltak's way as the author of the engine PR and/or to @dacharya64 in case of time availability :-)

For previous reverted fixes (may be less relevant with later changes to the serialization system), see b1576fb.

[Cervator]

Note: This is now tied to MovingBlocks/Terasology#3490 instead - see it for details

[eviltak]

Now tracked by PR MovingBlocks/Terasology#3535.