refs #5226 inherited loadSQW from IFileLoader and initial registration
refs #5226 Hopefully implemented

though can not find a way to modify the list of acceptable extensions
refs #5226 Removed redundant code (and fix Unix warnings)
refs #5226 Minor change -- adding sqw to the list of known extensions.

Otherwise, when loading sqw, it complains about unknown extension when logging is done in debug mode
Merge remote-tracking branch 'origin/feature/5226_Loader4LoadSQW'