Add logging for curl activity

[thepurpleblob]

We had some issues with mysterious 613 HTTP codes coming back. Urkund support really wanted to see that data packets but there's no facility for this. It would be useful to have a log option to dump the data being sent to urkund at that being returned so that HTTP issues can be investigated.

[danmarsden]

interesting idea - the full returned response from the http request should be stored in the table but we're not logging the outgoing data in the same way.