Order child pages (#21)

* save ordering pages

* move to another collection

* requested changes. Code improvements

* add margin

* unit tests

* fix

* requested changes

* recursive method: create menu tree

* update comments

* fix bug

* requested changes

* move const

* fix error message on catch

* add migration

* rewrite to splices

* move methods

* testing put above method

* linter fix

src/utils/database/index.js

@@ -1,4 +1,5 @@
 const pages = require('./pages');
+const pagesOrder = require('./pagesOrder');
 
 /**
  * @class Database
@@ -142,5 +143,6 @@ class Database {
 
 module.exports = {
   class: Database,
-  pages: new Database(pages)
+  pages: new Database(pages),
+  pagesOrder: new Database(pagesOrder)
 };