Allow users to select one of several templates

[bkettle]

Templates such as "modern" "classic" or something would be good to have.

Would probably be best to abstract the templates into LaTeX classes to do this, but not strictly necessary.

[lclarkg18]

Would also be great to allow users to state a file to input their own template if they already have a style they are using. Not sure there is enough demand for this tough :)