Folder properties menu item

[Ben Bucksch]

We now have a menu item "Edit | Properties" in Mailnews, which accesses
the *folder* properties, no matter what is selected. This is IMO wrong -
- either it is context-sensitive and displays the msg properties, if the
thread pane has the focus, or
- it has to be moved to "File" (where all the other folder-related items
are) and should be renamed to "Folder properties...".