When uploading from FLEx don't delete old Dictionary unless update successful

[peteroatley]

We would like a change in the way that Webonary handles the dictionary update process from FLEx.
At the moment Webonary deletes the old dictionary data and then creates the new information. This means that if the update fails a blank dictionary appears on Webonary.

We would like this changed so that the new data is uploaded and checked for success before the old data is removed.