add fragment:place & add 'fragment.place' command

src/logic/scripting/lua/libs/libgeneration.cpp

@@ -45,6 +45,7 @@ static int l_load_fragment(lua::State* L) {
 
     auto fragment = std::make_shared<VoxelFragment>();
     fragment->deserialize(map);
+    fragment->prepare(*content);
     return lua::newuserdata<lua::LuaVoxelFragment>(L, std::move(fragment));
 }