This moves the handling of pipes to the new InterfaceTreeModel as well.
It also includes a new PathChooserDelegate and cache handling for adding
data to an interface list without putting it into storage
Change-Id: Id255a81161b4da517e26127abe8ea7f5eb36d55a
Reviewed-on: https://code.wireshark.org/review/18497
Reviewed-by: Roland Knall <rknall@gmail.com>