Theoldreader categories support in liferea git master

Git master now features categories support when subscribing to theoldreader.com accounts. As TheOldReader allows only level of folders nested folders are not possible. Still this allows to organize the feeds neatly. If you already have a subscription don't worry your feeds will be automatically reorganized without loosing any items. The TheOldReader category support will be first included in release 1.11.0