Test to reproduce an issue that occurs with python3.3 under macos10 only

This test passes fine under linux
split content caching into two layers

This is a reworked and improved version of content caching.
Notable changes:
- by default only raw content and metadata returned by readers are
  cached which should prevent conficts with plugins, the speed benefit
  of content objects caching is not very big with a simple setup
- renamed --full-rebuild to --ignore-cache
- added more elaborate logging to caching code
Merge pull request #1320 from smartass101/cache_raw_content

split content caching into two layers
Merge pull request #1313 from al-tonio/frenchdate

Test to reproduce problem with Python 3.3+ on Mac OS X only