Support saving of the Battle system state in the LSD file #1410
Description
The most critical part for supported #1341 and in general a "save everywhere" feature the system of the battle system must be serialisable.
For this purpose we could invent a new chunk in liblcf and write everything important concerning the battle system in there.
It could have some convenience limitations with well defined sync points where a save state will revert to when there is a save in-between. As usual the critical part will be getting the interpreter on-sync :/.
Example: When a battle action is executed the save will always store the state when the battle action started.