IPRO: make it pass all tests

- Enable InPlaceResourceOptimization only in the required location
- Hand over the response headers we received to our
  InPlaceResourceRecorder
- Invent and pass in a Date response header set to the current date
  to the InPlaceResourceRecorder, if none is given.
- Set the appropriate expire configuration in the test configuration
  as required to enable ipro and pass the tests
- Port handle_error_ from ApacheProxyFetch
- Update the 'blocking rewrite enabled' tests expectations for IPRO
Merge pull request #452 from pagespeed/oschaaf-ipro

IPRO: make it pass all tests