* nGraph compat updates

* Simplify op structure

* Add zero-dim elimination pass

* Add logical data conversion pass

* Add graphviz support

* Add implicit broadcast pass

* Elide unnecessary reshape ops

* Merge reshapes into convolutions

* Add winograd convolution support

* Allow three-input maxpool backprop

* Add concat elision

* Combine replication operations

* Elide unneeded replicates

* Style update