Map locale from modules into the save's locale

Map locale files located at locale/{lang}/{file} in a module to
locale/{lang}/{module-name}-{file} in the save. This additionally
support a shorthand notation by mapping locale/{lange}.cfg to
locale/{lang}/{module-name}.cfg.

Resolves #500.

test/file/modules/test/locale/en.cfg

@@ -0,0 +1 @@
+module-test=A Test

test/file/modules/test/locale/en/locale.cfg

@@ -0,0 +1 @@
+module-test-locale=Test Locale

test/host/patch.js

@@ -9,6 +9,27 @@ const patch = require("@clusterio/host/dist/src/patch");
 
 
 describe("host/patch", function() {
+	describe("class SaveModule", function() {
+		describe("static moduleFilePath()", function() {
+			it("Should remap locale files", function() {
+				const mappings = [
+					["locale/en/foo.cfg", "locale/en/test-foo.cfg"],
+					["locale/en/foo.txt", "locale/en/test-foo.txt"],
+					["locale/en/foo.txt.tmp", "locale/en/test-foo.txt.tmp"],
+					["locale/en/foo", "locale/en/test-foo"],
+					["locale/en.cfg", "locale/en/test.cfg"],
+					["locale/en.txt", "locale/en/test.txt"],
+					["locale/en.txt.tmp", "locale/en/test.txt.tmp"],
+					["locale/en", "locale/en/test"],
+					["locale/en/bar/foo.cfg", "locale/en/test-bar/foo.cfg"],
+				];
+				for (let [input, expected] of mappings) {
+					assert.equal(patch.SaveModule.moduleFilePath(input, "test"), expected);
+				}
+			});
+		});
+	});
+
 	describe("generateLoader()", function() {
 		let reference = [
 			"-- Auto generated scenario module loader created by Clusterio",

test/integration/patch.js

@@ -27,6 +27,14 @@ describe("Integration of lib/factorio/patch", function() {
 			let zip = await JSZip.loadAsync(await fs.readFile(savePath));
 			assert.equal(await zip.file("test/modules/test/test.lua").async("string"), "-- test\n");
 			assert.equal(await zip.file("test/modules/subdir/dir/test.lua").async("string"), "-- test\n");
+			assert.equal(
+				await zip.file("test/locale/en/test.cfg").async("string"),
+				"module-test=A Test\n"
+			);
+			assert.equal(
+				await zip.file("test/locale/en/test-locale.cfg").async("string"),
+				"module-test-locale=Test Locale\n"
+			);
 		});
 		it("should remove old modules in a save", async function() {
 			slowTest(this);