Pre-work for #457

[dleard]

Capturing some of the pre-work required for #457:

• [x] Determine shape of post-2017 swrs data for MeasuredEmissionFactor
• [x] Requirements gathering for post-2017 data capture
• [x] Assess impact of removing old Measured Emission Factor table on existing metabase questions & decide on a path (synthetic renaming in metabase vs new table)
• [x] Update AC in card #457