Revert to old realplume syntax for the plume prefabs

[zorg2044]

Goes back to the simplified MM syntax for the custom plume prefabs.

• Maintains compatibility with old versions of realplume core.
• makes no functional difference, the benefits of the syntax used on the new version are not relevant to the CryoEngines plumes as they're not meant to be used outside of this mod.
• Makes it more resilient to changes within realplume core.
• Makes it easier to possibly convert these into smokescreen configs that exist independently of realplume if so desired in the future. (Would require new sound FX and some additional MM housekeeping).

[ChrisAdderley]

Thanks for the update!