Change CFBundleTypeRole to match quicklookd's requirements

fixes [WARNING] Invalid CFBundleTypeRole value in file:///Applications/CoRD.app/Contents/Library/QuickLook/CoRD%20Quicklook.qlgenerator/ (Viewer - should be QLGenerator)
Merge pull request #47 from Elwisz/master

Change CFBundleTypeRole to match quicklookd's requirements