added support for blending features into the chromosome picture using GD::copyMerge
added support for blending features into the chromosome picture using GD::copyMerge

asherkhb/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,asherkhb/coge,asherkhb/coge,asherkhb/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge,LyonsLab/coge,LyonsLab/coge,LyonsLab/coge,asherkhb/coge