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 
I am simply following the spec outlined in [bug 1060461](https://bugzilla.mozilla.org/show_bug.cgi?id=1060461) which uses `uuid` as the label.