More authorization

Users  authorization
Routes:
    /users/index - User has edit for own account, admin has edit for all
    /users/n    - User has edit for own, admin has edit for all
    /users/n/edit - Admin has privs checkboxes, user does not
Improved site flow

Layout now includes session-aware header/footer
Header:
    Logged In As _ - Links to Logout and Profile
    Not logged in - Login and Signup links
Footer:
    Logged in as mod - Link to posts
    Logged in as admin - Link to users

Also disable posting when not logged in