Provide better feedback when cannot open archive

[pointybeard]

Currently a generic error message is returned when opening of the zip archive fails:

The archive uploaded could not be opened. Please check it is a valid ZIP archive and contains CSV data.

This is not particularly helpful as there are many possible reasons it cannot be opened.

It should be more specific and based on the actual reason for failure.

[pointybeard]

Often this will be due to a missing manifest/tmp folder. It should be create automatically if it missing. Creating issue #3 for this.