consolidated roms re-imported if library is scanned after a consolidation

[Raphael P]

Status : If a game library was previously consolidated and that same library has to be re-scanned, ie if a new game rom was added to it, then all the duplicate roms will reappear in the games list.

Feature request is to give the choice to the user (checkbox before the scan starts), to allow him to decide if LB has to skip all the games that were previously consolidated or not.