Add an exception on import to ignore .nkit on filenames.

[Phil Stone]

There is currently some fuzziness in terms of games being successfully identified and scraped when they have the extension .nkit.iso or .nkit.gcz.

NKit is a fairly new compressed file format that has become popular for GameCube and Wii titles and has gained popularity as a choice for importing into LB.

Having the import process ignore .nkit in the filenames would ensure all these file formatted games import successfully without having an impact on any other platform.