Add Emulators over Uncertainties

[lbfinkbeiner]

This will primarily be a feature for the scenario processor, because all the machinery is already there. All we need to do is:

• Build a validation LHC with good minimum separation
• Request 5000 power spectra from the emu over the validation LHC
• Request 5000 power spectra from CAMB over the validation LHC
• Train a second emu to predict the deltas (or was Ariel requesting some other metric?)
• Use its output either to try to increase the accuracy of the first emu (this might require some new linking code in UI) or simply to predict what CAMB's error would be in some region of the parameter space...