Issue #1141 - When Accept header or Accept-Charset header has invalid QualityFactor we throw.

Issue #1141 
Fix: Imitating the same behavior as it is in WebApi. We ignore the entire header even if one part of it is invalid.
Yes. I had a discussion with @harshgMSFT on this. While we can choose to ignore only the invalid part of the header or throw an error, we chose the current implementation because WebApi follows this method.