Allow proper local modifications to themes.js

* themes.js is no longer published with the project. So it will not be overwritten
  on composer updates of the Magento framework
* Original themes.js becomes an example/template
* themes.js is managed to app/etc - just like env.php

Author: amenk

.gitignore

@@ -11,6 +11,7 @@ atlassian*
 /app/config_sandbox
 /app/etc/config.php
 /app/etc/env.php
+/app/etc/themes.js
 /app/code/Magento/TestModule*
 /lib/internal/flex/uploader/.actionScriptProperties
 /lib/internal/flex/uploader/.flexProperties

app/etc/themes.template.js

@@ -0,0 +1,59 @@
+/**
+ * Copyright © 2015 Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+'use strict';
+
+/**
+ * Define Themes
+ *
+ * If you are working with grunt for frontend development,
+ * copy this file to themes.js and configure your custom themes.
+ *
+ * If grunt is not used, you can ignore this file.
+ *
+ * area: area, one of (frontend|adminhtml|doc),
+ * name: theme name in format Vendor/theme-name,
+ * locale: locale,
+ * files: [
+ * 'css/styles-m',
+ * 'css/styles-l'
+ * ],
+ * dsl: dynamic stylesheet language (less|sass)
+ *
+ */
+module.exports = {
+    blank: {
+        area: 'frontend',
+        name: 'Magento/blank',
+        locale: 'en_US',
+        files: [
+            'css/styles-m',
+            'css/styles-l',
+            'css/email',
+            'css/email-inline'
+        ],
+        dsl: 'less'
+    },
+    luma: {
+        area: 'frontend',
+        name: 'Magento/luma',
+        locale: 'en_US',
+        files: [
+            'css/styles-m',
+            'css/styles-l'
+        ],
+        dsl: 'less'
+    },
+    backend: {
+        area: 'adminhtml',
+        name: 'Magento/backend',
+        locale: 'en_US',
+        files: [
+            'css/styles-old',
+            'css/styles'
+        ],
+        dsl: 'less'
+    }
+};

dev/tools/grunt/configs/themes.js

@@ -5,50 +5,9 @@
 
 'use strict';
 
-/**
- * Define Themes
- *
- * area: area, one of (frontend|adminhtml|doc),
- * name: theme name in format Vendor/theme-name,
- * locale: locale,
- * files: [
- * 'css/styles-m',
- * 'css/styles-l'
- * ],
- * dsl: dynamic stylesheet language (less|sass)
- *
- */
-module.exports = {
-    blank: {
-        area: 'frontend',
-        name: 'Magento/blank',
-        locale: 'en_US',
-        files: [
-            'css/styles-m',
-            'css/styles-l',
-            'css/email',
-            'css/email-inline'
-        ],
-        dsl: 'less'
-    },
-    luma: {
-        area: 'frontend',
-        name: 'Magento/luma',
-        locale: 'en_US',
-        files: [
-            'css/styles-m',
-            'css/styles-l'
-        ],
-        dsl: 'less'
-    },
-    backend: {
-        area: 'adminhtml',
-        name: 'Magento/backend',
-        locale: 'en_US',
-        files: [
-            'css/styles-old',
-            'css/styles'
-        ],
-        dsl: 'less'
-    }
-};
+try {
+    module.exports = require('../../../../app/etc/themes');
+} catch(err){
+    var e=new Error("Please configure your themes in app/etc/themes.js - start with copying themes.template.js");
+    throw e;
+}