[pvr] re-add recordings view state handling on a per directory level

As reported in our forum http://forum.kodi.tv/showthread.php?tid=210142 it's currently impossible to select and store a different sort order (in general different view state options) for each directory in the recordings window.

We've changed the view state handling to be global for all PVR windows, which makes sense for the channel, guide and timer window, but I understand the need for a more flexible handling in the recordings window. So this re-adds a view state handling on a per directory-level basis in favor of a per directory basis.

@Jalle19 and @opdenkamp if you look at the forum thread did you think we should handle this as a bugfix?