Details view: Expand the name-column like in Dolphin 1.x

With the new view-engine the name-column always has been expanded
to the maximum width of all available names. But this makes it
impossible to see other columns without scrolling when having long
filenames, so per default the Dolphin 1.x behavior has been applied
to the new view-engine so that the name-column-width gets decreased
to be able to show the other columns.

This patch will be released with KDE applications 4.8.2. For
Dolphin 2.1 (KDE applications 4.9) user-modified widths of the
columns will be remembered per directory also between different
sessions.

CCBUG: 264434