Validating the GNILC template: Redux

[brandonshensley]

In the course of using the d9 and d10 models, it has been noted that these models have more B-mode power at ell~80 in the Southern Hole than is measured by BICEP. I've put together a notebook with @delabrou investigating this issue, and my main takeaways are:

1. The difference comes from the Planck dust polarization templates used, not the post-processing work (e.g., adding small scales, log pol tens, etc.). I find roughly the same BB amplitudes in the raw GNILC templates as I do in the d9 and d10 models. @delabrou thinks it is possible that the excess power is residual noise not removed by GNILC.
2. It is unclear why the MKD model looks so different, other than a different template was used. It is not a priori clear that d12 (MKD) is any better than d10, but a posteriori whatever was used for MKD seems to agree better with BICEP measurements.

I'm not quite sure what to do here: the differences are quite large and have an impact on r forecasts. @zonca @bthorne93 @giuspugl @seclark @NicolettaK Thoughts?

Note also this old issue on validating these templates.