Update log format for ci_ip_diagnostics - ISO8601 timestamp is now first field

The format for the `Diagnostics.log` files have changed to include a timestamp as the first field:

```
2013-09-03T00:35:36.587+01:00,502624656,LEVEL1,New/Accepted/ITP,00:35:36.487,62.3988,100,1
```

This PR updates the parsing to use this.

@dpb587 - we need to co-ordinate when this gets rolled into the logsearch-ppe cluster.

The parsing is [currently being done in the diagnostics shipper](https://github.com/cityindex/logsearch-on-aws/blob/master/ppe-cluster/shippers/diagnostics/config/filters.erb); but this should be removed when this change has been deployed in favour of the parsing getting done by the indexer