Guess parser (name guess)

## Guess parser (name `guess`)

This is a special parser that picks the actual parser to use based on the content type, the content bytes or the content identifier. The content name can be either from a local file or from a URI.

If the protocol that delivered the content (such as HTTP) provided a Content Type (aka MIME Type) then this will be the primary means for identifying th ecotnent.

The secondary means to identify the content are the bytes of the content (if available), otherwise the content identifier is used, which is the least reliable.