Non-behavioral changes to CloudEventFormatter
Non-behavioral changes to CloudEventFormatter

- Reorder the method declarations to be consistent (with an eye to
  batch mode):
  - Abstract methods before virtual
  - Sync before async
  - On a per-mode basis, decode before encode
- Fix the location of "asynchronously" within the documentation
  (it was on the wrong method)

Signed-off-by: Jon Skeet <8a9602d66334021c18cbf0bdb2fa15f4cb6de9df@google.com>

cloudevents/sdk-csharp,cloudevents/sdk-csharp