The 2df test is implemented. Now, if analysis_type=2df, then the regression model includes P_AB and P_BB (probabilities of having genotypes AB and BB) and presence of association is tested jointly for P_AB and P_BB. We still need to test it on the possible bugs.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/genabel@1610 edb9625f-4e0d-4859-8d74-9fd3b1da38cb