Better batch design

[siddharthab]

Streams currently only support continuous flow as volume, mass or molar units per hour.

This leads to non-obvious unit designs when operating in batch mode. For example, a StirredTankReactor should be able to take its feed from a StorageTank and Pump combination to load much faster than what the continuous flow mode would allow. The current implementation of batch design for StirredTankReactor assumes that the continuous feed is being used to load one reactor at a time. This is inefficient utilization of each reactor, especially if you want to stagger fewer number of reactors, or if residence time in the reactors is very long.