Correcting bug where optim's finite difference estimate for gradient failed mysteriously when fitting generalised logistic model to some of Marion's datasets.  Tidied up code to explicitly handle different scenarios for fixing g and fixing v (regular logistic model).  Not certain why this has made a difference.

Also, re-introduced modelFit argument to qfa.fit, optionally avoids generating fitnesses based on curve-fitting.  Saves time if only interested in e.g. nAUC or K.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/qfa@618 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Functions to help generate timecourse photographs for all replicates of a given strain in an experiment.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/qfa@619 edb9625f-4e0d-4859-8d74-9fd3b1da38cb