bug 1066058; add Support Reason API crashstorage type

*Preamble: This PR is primarily submitted for discussion purposes (I expect more work to be necessary).*

This adds the `SupportReasonAPIStorage` class which is a sub-class of `BotoS3CrashStorage`; functionally speaking, the former is basically a *highly lossy* implementation of the latter.

cc @twobraids 
Oh. I see. This is not your invention but it's in line with the rest of the API. 

However, I insist that this needs to become configurable. Otherwise you'd end up using the same bucket name in stage and in prod and then we'd mix streams. 

So, perhaps keep this method but instead change to something like this:

```python
# note, no longer a @staticmethod
def _create_bucket_name_for_crash_id(self, crash_id):
    return self.config.bucket_name
```