[core] Adding FilterCube to refactor code for filter.
[core] Adding FilterCube to refactor code for filter.

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