New style: Coventry University Harvard

This is an alternative implementation of Coventry University's Harvard style guidelines. I found multiple issues with the existing Coventry style sheet and when I came to look at them realised it was significantly easier for me to start with code that I know and have used extensively (University of Birmingham) than to try to correct the existing style sheet.

Usage notes at http://www.oak-wood.co.uk/oss/coventry-harvard-csl