Cleanup layout template

* Remove incorrect id
* Remove a variable no longer needed
Don't nav to current post from one of its pages

* Add a check that the first previous or next post found in the list
doesn’t match the title of the current post
* Links were showing that would take a user back to the first page of
the current post, rather than the previous post
Move next and previous post nav to header

* Beneath the title the links clashed with the pagination ones
* In the header they are more prominent
* Remove old comments, admin and wordpress CSS hacks