Create "meta" table, maintain various stats useful for troubleshooting

[deoren]

The content below is pulled from an old local todo.txt file. I've changed my mind on some of the details, but posting here as-is for now. I plan to loop back later and refine the details before working to implement this.

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• Create meta table for logging when any other table was last updated (presumably we won't be wholesale nuking the existing tables on each run by this point)

  • meta.db_last_modified
  • meta.db_revision (auto-increment for every update to database)

• Create TRIGGER to handle updating meta.db_last_modified column when any other table is modified

  • possibly have this same TRIGGER handle updating the meta.db_revision column too