Make a PPACalculator that inherits the WCalculator
In PPA calculations W is parametrized and one does not work with the full W_wGG matrix. Due to the different nature of these calculations it makes sense to make a PPA Calculator that inherits the Calculator but overwrites the _calculate() and calculate() methods. To solve this issue one should:
- Make a PPA calculator as described above
- Go through and document the meaning of the different terms in the PPA code (Omega_GG, R_GG, W_GG) in the code.