Add show/revert interpolations ability to SBMax

Would be beneficial to show soundings that were interpolated and then have the ability to restore them to the original soundings. So SB max chould have a view option like show deleted that should show the original recorded location of interpolated soundings and then add the ability to put them back much like undeleted. This is most needed for sounders that do NOT have an echogram. Hitting CTR Z works but not very well if you have moved to other lines and find something was a real thing and not an artifact.