Feature: Protected articles

Expanding #338 to a more flexible feature.

`bool IsProtected { get; set; }`

This property should not allow for the following:
- renames
- deletions
- content changes.

By default this value should be false for all articles except Home page.
could be modified only by an admin for each article.

Possible issues when merging #338 :
- home page needs to be differentiated for UI changes (hide back button)