new MARK feature | mod avg individual covariates

[cooch]

Gary has introduced a very helpful new feature in the latest MARK build -- the ability to model average real parameter estimates over a range of continuous individual covariates. In fact, there are a couple of different ways to approach this model averaging -- see section 11.8 in chapter 11 of the MARK book. [Said text is not in canonical form yet, but the basics are in place...]