make the "show recent directory path breadcrumb" file listing feature optional and off by default.

[williamstein]

See discussion at #6802

This feature is very nice for power users... but is NOT standard behavior in file managers, and by default there is no indication at all that a slight variation in font means something. This should definitely be off by default, but something power uses can enable (since, e.g., I love it... but I also know what it means).