Navigation Sidebar

[NGPixel]

Objective

A customizable navigation sidebar that can alternate between static menu items and automatically generated list of pages at the current level.

### Tasks
- [x] Browse mode
- [x] Static mode
- [x] Static - Add / Edit / Delete / Rearrange Items
- [x] Static - Per path (exact / starting with) navigation items
- [x] Static - Nested Menus
- [ ] Admin - View list of all navs

[ajukadavid]

@NGPixel can i work on this issue?

[pping]

If there are too many pages, it will be very painful to rebuild the navigation bar. I think the most important thing is to support the "import" and "export" functions of the navigation bar, which will be helpful for backup and data migration.