Clean up series plugin to operate with entries and db objects more.

git-svn-id: http://svn.flexget.com/trunk@3253 3942dd89-8c5d-46d7-aeed-044bccf3e60c
Fix imdb genres unit test.

git-svn-id: http://svn.flexget.com/trunk@3254 3942dd89-8c5d-46d7-aeed-044bccf3e60c
Fix crash with --series after recent series refactoring.

git-svn-id: http://svn.flexget.com/trunk@3255 3942dd89-8c5d-46d7-aeed-044bccf3e60c