Improvements to Upsert

[sijandh35]

• If something goes wrong during the feature save, the error log should be clearer, possibly by including it in the downloadable CSV file.
• The schema validation description should be more user-friendly.
• When running an upsert, it would be useful to include a date in the filename so users can easily identify the most recently uploaded file.
• If a schema validation error occurs, it should be reported in the CSV file to clearly show the error to the user.