Velocities for ASCII postprocessor
Tigstu suggested to read/write velocities instead of unit-discharges. Although it is feasible to do that, it might slow down the computation because we should create auxiliary variables and the writing wouldn't be as straightforward as it is now. We can discuss if we can do as a part of the postprocessor instead. We discussed it during the meeting. I think we can keep using unit discharge (hu & hv) in all Binary files. However, when we are saving the results in ASCII and other outputs, we should do velocity (u, v) instead.