indicate sort-field and bind "<" and ">" for top-like sort control

[linuxcaffe]

This is a two-part feature request, the first part "indicate sort-field" is to embolden the field-header of whatever field the list is being sorted on. The second part "bind "<" and ">" for top-like sort control", is to bind these keys to mean "< sort on the column to the left" and "> sort on the column to the right"

This behavior is modeled after the command-line utility "top", and I think that with an additional "R" to mean reverse sort, this could greatly enhance list-browsing.