feat(RFISensitivityMask): add a new RFI excision task
feat(RFISensitivityMask): add a new RFI excision task

This task uses searches for outliers in the system sensitivity data
(which seems to be a more effective space) to identify RFI.

fixup RFI routines such that it works when parallelised and with Seth
and Saurabh's new code

radiocosmology/draco,radiocosmology/draco