#497 grepwin: Sort suggestions by most recently used

[voidpointer]

At the moment, all of the [/] buttons show suggestions in (I think) alphabetical order. I think it would make more sense to list them by date used in descending order. Meaning, the most recently used searches would appear at the top. The last-used search suggestion would appear at the bottom of the list. For existing older search suggestions, if the user selects that suggestion and searches with it, it's "last used" date should be updated to "now" and it should appear at the top of the suggestion list next time.

This change should apply to all fields where suggestions can be provided. Furthermore, I think this should become the new default behavior. However, I'm not opposed to keeping alphabetical by default and allowing this to be turned on via an option if you feel that would be better.