Multi-Channel Surface Effects

[braxbro]

2.0 brought us the tremendously useful LuaSurface :: global_effect property, as well as the ability to have effect receivers that receive from or ignore surface module effects.

However, if you're trying to create things like, say, custom weather that affects certain buildings differently, being able to have more than one channel for surface effects would be extremely beneficial. Thus, I propose adding the following property:

EffectReceiver::surface_effect_channel (uint8)

which would determine which set of global_effects to apply. Similarly, global_effect would probably end up needing to become an array. (and thus be pluralized lol)

Thanks for the awesome game!