Update ManagerController.cs

[amigre38]

The modifications to :

• handle the remove of _files.tumblr when a blog is removed.
• Avoid the reset of downloaded items in case the blog already exists in the list
• Avoid the error when saving the downloaded index at the end of process if the name contain the full path of the file instead of the blogname only.

[amigre38]

I see you already do the job for two of the things i do ;) there's only the latest item about the files that contain in some case the full path ".\blog\index\blogname.tumblr" instead of just only the "blogname" and you are all set and my code is of no use lol