Bidirectional Variants of Networks

[alex-mckenna]

For basic systolic networks, the library should provide unidirectional and bidirectional variants where possible. I suspect that these commonly will use the same configuration types as their unidirectional counterparts, but would need their own instances in order to correctly connect signals together. Bidirectional networks to be implemented:

• [ ] Bidirectional pipelines
• [ ] Bidirectional rectangular networks
• [ ] Bidirectional trees
• [ ] Bidirectional lattices

[alex-mckenna]

Another concern: bidirectional networks may be closed at one end, i.e. data that flows on the back edge is generated by cells instead of by cells + external inputs. This may be desirable for actions on tree-like structures where the computation can be viewed as splitting followed by merging