Let users choose theme for parts that has no sections setting

When the sections module is active users theme choice no longer works. For parts that have a sections setting this is what you would expect but not for other parts I think.

This patch seems to allow user theme settings. It also correct the return path after you delete a section be removing "/list" from the url.

P.S. Does caching not work with parts that have sections settings or for the whole site when you use this module?