Taking WF Gradients and Laplacian computation out of updateBuffer

**Is your feature request related to a problem? Please describe.**
Current updateBuffer does both some computation and buffer operation. This is a sick design choice.

**Describe the solution you'd like**
Move all the computation of WFC G and L evaluation out of updateBuffer and put it in evaluateGL API.
Then the Kinetic evaluation is responsible for calling evaluateGL.
We have to do this change regardless how we redesign the buffer.