Settings can now be taken from separate file with local override.

* Various settings in settings-nvr.js module
* settings-nvr-local.js can override settings-nvr.js
* settings-nvr-local is unchecked file
* Both files can be straight maps, or functions returning maps
* webpack env and args available to those functions

webpack/NVRSettings.js

@@ -0,0 +1,51 @@
+// vim: set et ts=2 sw=2:
+//
+const path = require('path');
+const Settings = require('./parts/Settings');
+
+/**
+ * Exports a sub-class of Settings specifically for the Moonfire NVR project.
+ *
+ * Gives us a simpler constructor that encapsulates the names of the expected
+ * settings files.
+ *
+ * Provide some convenience member variables:
+ * config {object} Map of the original settings configuration
+ * values {object} The values map of the settings that were configured
+ *
+ * @type {NVRSettings}
+ */
+module.exports = class NVRSettings extends Settings {
+  /**
+   * Construct an NVRSettings object.
+   *
+   * This object will be a subclass of Settings, with some extra functionality.
+   *
+   * Initializes the super Settings object with the proper project root
+   * and named settings files.
+   *
+   *  @param {object} env        "env" object passed to webpack config function
+   *  @param {object} args       "args" object passed to webpack config function
+   * @param  {String} projectRoot Project root, defaults to '.' which is
+   *                              usually the directory from which you run
+   *                              npm or yarn.
+   */
+  constructor(env, args, projectRoot = './') {
+    super({
+      projectRoot: path.resolve(projectRoot),
+      primaryFile: 'settings-nvr.js',
+      secondaryFile: 'settings-nvr-local.js',
+      env: env,
+      args: args,
+    });
+    const config = this.settings_config;
+    // Add some absolute paths that might be relevant
+    this.settings = Object.assign(this.settings, {
+      _paths: {
+        project_root: config.projectRoot,
+        app_src_dir: path.join(config.projectRoot, this.settings.app_src_dir),
+        dist_dir: path.join(config.projectRoot, this.settings.dist_dir),
+      },
+    });
+  }
+};