Einasto Profile #52
Description
Implement the Einasto profile module. The new module should live here astropaint/profiles/Einasto.py. The structure can be identical to NFW. Essentially the only difference would be the rho_3D function.
The other profiles (kSZ, deflection_angle, etc) should be factorized into a separate module and then called into NFW and Einasto. Will open another issue for this soon.