Make menus dynamic

[uberswe]

Currently there is no way to manage menus. It would be good if menus are stored in the database similar to how pages work.

[uberswe]

This task is more complicated than I initially thought but I am making some progress. Some things that make this complex is that you can have several menus, I consider each section a MenuSection and each section has one or more MenuItem. A MenuItem may or may not be shown based on the following checks.

• The current user has permission to see the item
• The current user is authenticated
• A context variable, such as site id, is needed to display this item
• A site setting or global setting can show or hide the item