[Reviewer: Alex] Add AS name to iFC-related SAS logs; reduce number of iFCs sent to SAS

As part of my assault on https://github.com/Metaswitch/sprout/issues/538, I've added the AS's URI to the SAS logs.

While doing this, I noticed:
* the processing for the "invalid iFC" SAS log could be trivially simplified
* malformed IFCs both an "invalid IFC" and an "IFC does not match" log, which seemed redundant
* we logged the body of the IFC when we started processing, when we noticed it was invalid, and when it doesn't match, which seems like a pointless amount of load on SAS - I've reduced it to just log the IFC when we start processing it

One thing I didn't implement (but might be quite nice) is a diagram of how iFC logic decisions happen, something like:

```
Group 1: AND true, false, true -> false
Group 2: AND true -> true
Overall: OR false, true -> true
```

I think this would be quite useful in understanding/debugging why iFCs are matching/not matching when it's not expected - what do you think?

Not tested - pass back to me with any comments and I'll test it all before merging. I propose to test by:
* creating an IFC that should match (e.g. the default MMTEL IFC with an INVITE) and checking that the logs are correct and the IFC is only logged once
* creating an IFC that shouldn't match (e.g. the default MMTEL IFC with a REGISTER)  and checking that the logs are correct and the IFC is only logged once
* creating an IFC that's invalid (e.g. by loading one with an invalid regex directly into Homestead) and checking that the logs are correct and the IFC is only logged once
This should be a separate event probably (one that doesn't take a server name parameter).