mappings/Veg+-VegCore.csv: /_alt pass through mappings: Removed comment because the two-level mapping propagates it to all fields ending in /_alt, even though it doesn't apply to them, causing the main VegBIEN map and several datasources' maps to change unnecessarily. Also, the comment is not completely accurate because /_alt pass throughs are now used primarily to support idempotent self-joins of Veg+-VegCore.csv.
mappings/Veg+-VegCore.csv: /_alt pass through mappings: Removed comment because the two-level mapping propagates it to all fields ending in /_alt, even though it doesn't apply to them, causing the main VegBIEN map and several datasources' maps to change unnecessarily. Also, the comment is not completely accurate because /_alt pass throughs are now used primarily to support idempotent self-joins of Veg+-VegCore.csv.