Updated add data form to use addLayer function and properly set blend mode.
Updated add data form to use addLayer function and properly set blend mode.

openconnectome/NeuroDataViz,neurodata/NeuroDataViz,openconnectome/NeuroDataViz,openconnectome/NeuroDataViz,neurodata/NeuroDataViz,neurodata/NeuroDataViz