More specific error messages

[wkdewey]

"Error transforming ES" and the like needs to be changed to display a more informative error message.

[wkdewey]

• Errors when validating the schema need to be checked for correctness, and include more detail on how to correct the error.
• Server errors (such as 400 Bad Request) should be output with the full message from Elasticsearch, which often indicates more specifically what data ES deems to be malformed.