Simplify page headers and footers

A minor visual spring clean, to bring the Service Manual styles closer to the rest of GOV.UK

The biggest change is the removal of the phase tags from below the page titles.

![image](https://cloud.githubusercontent.com/assets/1590604/2840887/1dfdf684-d05e-11e3-8b24-b60517409440.png)

Analytics shows that they're rarely clicked on. They've never been mentioned in any survey or feedback. When prompted in user testing, users struggle to correctly interpret them or understand their value. 

Most guidance is potentially relevant to any phase. If it's important for users to understand which phase some guidance is related to then this can be done within the content itself.