Fix modification time disappearing from context data and handling missing value
Added test for double population issue 449
Pep8 clean up
Moved dexterity item creation to Fixture setup - fixes test when profile was not ready soon enough
Refactor tests

Remove cluttering and move content type creation to the test to speed up execution time.
Skip test on Plone < 4.3
Merge pull request #454 from collective/issue_449

Fix double dropping content