Faster method to calculate total Chern number

[sp94]

Currently we have Wilson loop methods which are very general and can be used to calculate

• Total Chern number of a set of bands
• Some symmetry-protected Chern numbers
• Multiband/non-Abelian Berry curvature

However, when calculating the total Chern number

1. you must manually count the winding of the Wilson loop spectrum to find the Chern number
2. using the Wilson loop winding method is slower than other 'plaquette' based methods

We should add a direct Chern number calculation based on plaquettes, as in eg a. Fukui et al https://doi.org/10.1143/JPSJ.74.1674 b. Zhao et al https://doi.org/10.1364/OE.380077