* Wrap methods of ProcessFeedService::ProcessEntry in classes

This is a change same with 425acecfdb15093a265b191120fb2d4e4c4135c4, except
that it has the following changes:

* Revert irrelevant change in find_or_create_conversation
* Fix error handling for RemoteActivity

* Introduce Ostatus name space

possibly others when expected. Add some tests for it

* Likely fix #2458, fix #2031 - handle out-of-order deletes for statuses

If a delete arrives before the original status, cache that information
for 6h, and if the original status arrives in that window, ignore it

* Add test case

In #2110, a new attachment type "unknown" was introduced for
attachments that were rejected due to a domain being blocked using
reject_media. However, the "type" field was never set to "unknown"
because a default value of "0" (image) is set for that column,
causing the `type.blank?` expression to always equal false.

This version uses type_changed? instead, causing the type to be set
to "unknown" unless a type has been explicitly set. This introduces
a small change in behaviour causing the type to be set to unknown
before paperclip calls `before_post_process`. Presumably this
behaviour is more appropriate than the current one because the
attachment type has not been determined by that point.

Included are new tests for `ProcessFeedService` and
`UpdateRemoteProfileService` which now check that remote media is
downloaded for non-blocked domains and is rejected for others.

* Instead of parsing shared status contents verbatim, make roundtrip
to purported original URL. Confirm that the "original" URL is from the
same domain as the author it claims to be from.

* Fix obvious typo, add comment

* Use URI look-up first

* Add test, update Goldfinger dependency to make less useless HTTP requests per Webfinger lookup