* Fix charset encoding & MIME type handling
Character set (ie what we call "encoding") is part of the Content-Type,
*not* the Content-Encoding, which specifies compression (e.g. gzip).
This correctly sets the character set encoding as well as cleaning
the MIME type so that additional parsing doesn't need to be done
downstream (and removes that code).
* Use "text" instead of "text/line-based" as default fallback format
The TextLineBasedGuesser only tries a limited number of
formats (CSV, TSV, fixed), so we can't get out of that hole to
find JSON, XML, etc.
Start with a more general format instead to improve our
guessing odds.
* Support content type Structured Name Syntax Suffixes (+json +xml)
If we can't find a fully specified content type in our lookup,
fall back to just the suffix (which is registered with a leading +)
Fixes#2800Fixes#2805