Update File Options "paste" behavior to use insert-above instead of overwrite

To be more consistent with the paste key behavior elsewhere in SCFG,
make the file options (Viewable Files, Testable Files, Download Events,
Extractable Files, Compressible Files, and Transfer Protocols) menus handle
paste (Ctrl-V, F6) key by inserting the copied or cut item above the current
selection rather than overwriting the current selection.

Fixes issue #616