refactor & add structures.json

src/world/generator/GeneratorDef.cpp

@@ -0,0 +1,11 @@
+#include "GeneratorDef.hpp"
+
+#include "VoxelFragment.hpp"
+
+GeneratingVoxelStructure::GeneratingVoxelStructure(
+    VoxelStructureMeta meta,
+    std::unique_ptr<VoxelFragment> structure
+) : structure(std::move(structure)), meta(std::move(meta)) {}
+
+
+GeneratorDef::GeneratorDef(std::string name) : name(std::move(name)) {}