[viz]: support for multiple channels
[viz]: support for multiple channels

neurodata/ndstore,openconnectome/open-connectome,openconnectome/open-connectome,openconnectome/open-connectome,neurodata/ndstore,openconnectome/open-connectome,neurodata/ndstore,neurodata/ndstore,openconnectome/open-connectome,openconnectome/open-connectome