Port fix for Update how certain cache directives are handled to 1.1.x

[JunTaoLuo]

We'll need to port back part of the fixes in #88 back to 1.1.x.

At the minimum we'll need the fixes to:

• Always add the IResponseCachingFeature before calling the next middleware Cache-Control: no-cache breaks the middleware #81
• Use If-Modified-Since instead of the wrong If-Unmodified-Since header for conditional requests

Also potentially consider

• handling of proxy-revalidate cache directive and handling of max-stale without specified limit

[JunTaoLuo]

cc @muratg

[Eilon]

This patch bug is approved. Please use the normal code review process w/ a PR and make sure the fix is in the correct branch, then close the bug and mark it as done.

[Eilon]

@muratg please assign.

[JunTaoLuo]

Patch merged. Leaving the issue open since version numbers will need to be updated.

[JunTaoLuo]

Changes merged. Updating version numbers now.