Replace Hotpatch with save patching

Remove Hotpatch and implement a save patcher in its place.  The save
patcher takes a normal Factorio save and adds modules to it that's
loaded by a generated control.lua file.  This greatly reduces the
difficulty of adding an existing game to Clusterio and using scenario
code in plugins.

The mechanism for selecting what code to patch into the saves from
plugins is temorary and expected to change with #220.

test/integration/patch.js

@@ -0,0 +1,31 @@
+const assert = require("assert").strict;
+const fs = require("fs-extra");
+const jszip = require("jszip");
+const path = require("path");
+
+const factorio = require("lib/factorio");
+
+
+// The server integration test is required to run before this one
+require("./server")
+
+describe("Integration of lib/factorio/patch", function() {
+	describe("patch()", function() {
+		let savePath = path.join("test", "temp", "integration", "saves", "test.zip");
+		it("should patch a freeplay game", async function() {
+			await factorio.patch(savePath, [{
+				name: "test",
+				files: [{ path: "test.lua", content: "-- test" }]
+			}]);
+
+			let zip = await jszip.loadAsync(await fs.readFile(savePath));
+			let content = await zip.file("test/modules/test.lua").async("string");
+			assert.equal(content, "-- test");
+		});
+		it("should remove old modules in a save", async function() {
+			await factorio.patch(savePath, [{ name: "test", files: [] }]);
+			let zip = await jszip.loadAsync(await fs.readFile(savePath));
+			assert.equal(zip.file("test/modules/test.lua"), null);
+		});
+	});
+});