Better and safer refreshing of selected results (fixes #48)

Fixes an issue where selected files weren't being refreshed when selected with mouse, then keyboard was used (and vice versa). Selecting multiple files with mouse, then using keyboard to move up or down, then right clicking would result in previous selection being reselected.

Also addressed issue where if you search and select a file (right click and open) then do another search and select a file on the same row, the file from the previous search would be silently selected (copy, save as, delete would modify the previous file).