The org.gnome.nautilus.preferences default-sort-order key is a currently
hidden-from-UI preference that should be honored by all views, if no
custom order is specified in the current location's metadata.

However, for this to work, two enums must be kept in sync between the
code and the schemas. This has not been happening since the introduction
of the Starred files feature.

To fix this, restore the sort order according to settings, and make
starred take the place of trash-time, which is non-sensical as default
for all folders.

Forthermore, to prevent this from breaking again, add documentation to
both enums.

Fixes GNOME/nautilus#636