Replace custom build system with Gulp. (#259)

* Use Gulp for build system, tsc to compile files, part 1.

* Hide tsc-generated files from VSCode.

* Add a private build-utilities package, leveraging Gulp.

* Synchronize files with the same name.

* Capture whether files change.

* Try invoking tsc without overwriting the config.  (Not helping much.)

* InvokeTSC, PushAndPopDirs

* First complete Gulp-based build.

* clean before build

* Run prettier in the code generation directory via Gulp.

* Remove the custom build system in favor of Gulp.

.vscode/settings.json

@@ -0,0 +1,12 @@
+{
+  "files.exclude": {
+    "packages/v2-es-membrane/_*/**/*.js": { "when": "$(basename).ts"},
+    "packages/v2-es-membrane/_*/**/*.js.map": true,
+    "packages/v2-es-membrane/build-utilities/**/*.js": { "when": "$(basename).ts"},
+    "packages/v2-es-membrane/build-utilities/**/*.js.map": true,
+    "packages/v2-es-membrane/gulp-utilities/**/*.js": { "when": "$(basename).ts"},
+    "packages/v2-es-membrane/gulp-utilities/**/*.js.map": true,
+    "packages/v2-es-membrane/Gulpfile.js": true,
+    "packages/v2-es-membrane/Gulpfile.js.map": true,
+  }
+}