! http, can: support for custom status codes, fixes #564

Breaking behavior: HttpSuccess + HttpFailure are not public API
any more.
Merge pull request #577 from jrudolph/i/564/custom-status-codes

! http, can: support for custom status codes, fixes #564
! httpx: enable FEOU and FSOD to be interchanged in the usual cases, fixes #426

The idea is to
  - interpret application/x-www-form-urlencoded fields as text/plain so that FEOU can read
    it as well
  - interpret multipart form parts with content-type text/plain as strings that
    can be read from FSOD

This should make it much easier to change the form encoding on the client
without having to change anything on the spray side.
= docs: fix broken links and warnings
Merge pull request #580 from jrudolph/i/426/formFields-revamp

! httpx: enable FEOU and FSOD to be interchanged in the usual cases, fixes #426
! http: add HttpOrigin and use it for Access-Control-Allow-Origin and Origin headers, fixes #579
= http: reorder HttpHeader source code alphabetical
= httpx: fix Deflate reporting wrong number of remaining bytes, fixes #583

Before Deflate.decompress always assumed `inflater.finished()` was already
working on the last 1024-Byte chunk of input data when in fact it could be
anywhere else. The test-case was pathological because of its compressed size
being just a few bytes more than the internal buffer of 1024.
+ 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`
= servlet: don't leak exceptions while handling exceptions, fixes #586
Merge pull request #582 from jrudolph/i/579/improve-CORS-model

! http: add HttpOrigin and use it for Access-Control-Allow-Origin and Origin headers, fixes #579
Merge pull request #584 from jrudolph/i/583/gzip-problem

= httpx: fix Deflate reporting wrong number of remaining bytes, fixes #583
Merge pull request #587 from jrudolph/i/586/fix-exception-during-error-reporting

= servlet: don't leak exceptions while handling exceptions, fixes #586
= can: group commander dispatchs for easier instrumentation
Merge pull request #588 from ivantopo/easier-client-instrumentation

= can: group commander dispatchs for easier instrumentation
Merge pull request #585 from jrudolph/i/327/uploaded-filename

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