Reviewer - please discuss with CLZ first. only review top 2 commits (on contentview-columns branch).

Only in lists and the list of search results, add a new column containing the path to the item. We need the path in lists in order to distinguish two items with the same name. It's not enough to just have the breadcrumb, as it always requires you to select an entry first before you know where exactly it's located.

• A "Path" column should be added between the column showing the item's icon and name and the column showing its title.
  • We do not need this column in the "Messages" list in Pulse.
• It should be visible by default.
• If the path it shows is too long, abbreviate it using a middle ellipsis so that the beginning an the end is still visible.