+ httpx: create another layer of Unmarshallers, FromBodyPartOptionUnmarshaller, to be able to unmarshal from BodyParts (including headers), refs #327
! http(x): create FormFile as an easy way to access uploaded file information for forms, fixes #327
+ http: simplify creating MultipartContent from a Map of FormFiles, fixes #327
= docs: add documentation for `clientIP`
Merge pull request #585 from jrudolph/i/327/uploaded-filename

Various improvements for easier handling of file upload from forms, fixes #327