Anti-alias FIR Filter Discussion

[kkappler]

We are able to load these FIR filters. These tend to be anti-alias filters applied during digitizer decimation processes.

1. The filters applied to the E and H will in general be the same so that ratios and TFs will not be affected assuming the survey uses the same acquisition systems -- which is common but not true in general
2. If we do back these filters out we need to sort out the phase shifts and whether these are applied zero-phase, from the right or from the left. It is not clear how the filter application is referenced in Station XML .. there is a element in the XML, cannot find doc on what it means though

This issue relates to #34

[kkappler]

The AAF FIR filters are now working at least for the Quanterra data. The can now be applied or not applied by the kwarg include_decimation in channel_response_filter.py.