Looks like its too bloody hard. When you have a stupid intial view in your way

Can do any unwind or exit segue to ViewController due to intial view
and other stupid reasons.
Turns out it can be done.

By using navigation view controllers which store the hierachy of
viewcontrollers in an array it can return to the previous view
controller
All Equation Chapters Linked up to new Navigation Controller
Linked up the documents library, Added way to see credits page

The credits page however is not using ECSlider I will need to get david
to look into how this may be possible with Navigation View Controllers
Linked up the Document Viewer and the new Worked Examples Viewer

Now every view controller that is unique design wise has a its own view
controller and goes back along the story board to its respective
previous view the user was on, instead of going 'back' to the documents
browser. Currently the passing of data between the views isnt working
correctly this will be fixed later.
Removed custom segue's and linked up some more worked examples

removed all custom segues as they are no longer needed.
Merge branch 'Document-Viewer-gets-its-on-.m-and-.h'

Conflicts:
	EquationViewer.h
	EquationViewer.m
	Formulae.xcodeproj/project.pbxproj
	Formulae/ViewController.h
	Formulae/ViewController.m
	Formulae/en.lproj/MainStoryboard.storyboard