make farming use clone-node to alter drops, move waving=1 to default/nodes.lua

This request depends on minetest.clone_node() being added to builtin:

	
```lua
function minetest.clone_node(name)
	node2={}
	node=minetest.registered_nodes[name]
	for k,v in pairs(node) do
		node2[k]=v
	end
	return node2
end
```