Improve "Failed to identify table based on headers" log information

[patrick-troy]

The current logs that just say "Failed to identify table based on headers" are potentially too broad. It's not immediately obvious to identify which years should have which headers from our repository (there's lots of extra information and with the schema.diff files they only contain changes year on year rather than a full schema), so trying to identify the missing headers can be a tedious task. To fix this:

• In the repo we could create a table/readme file that simply shows all the expected headers for each year for each file. Then an LA analyst can much more easily cross-reference this to identify the missing headers.
• This file should be linked in the user upload page.