First pass at 'Ensuring Quality' piece

A first pass at pull together some thinking about Quality into a single place. I've put it within 'agile' and I think the primary audience is Service Managers but that it should be read by everyone.

I'm now away for a couple of weeks so suggest that someone other than me (@garethr?) would be best to review comments and suggestions for the piece.

If we add this we should then review the related content in other places, particularly the testing sections and the proposed new 'choosing a transformation partner' content as there is some overlap and we could helpfully consolidate it.

It may also be worth considering whether there should be a 'quality' or 'testing' section rather than placing this in agile. Our testing content seems rather spread out, though testing is part of everything so there are pros and cons to pulling it together.