Major UI overhall

Redesigned and finalised most of the pages re: the spec.
Add article delete functionality
Add support for post visibility

Allows a user to specify whether a post should be publicly visible
or only to Authors. Related view changes in 'Add article delete
functionality' commit.
Fix a bug where non-users could access article creation and deletion

Leftover from a previous commit.
Change copy on Author page

Removed 'Other' from the copy.
Cosmetic - Rename variable in ArticleDAOImpl