Allow naked OTF and TTF files, follow-up on #1860

This should not be needed for .qlgenerator or .prefPane, because
(like .app) those are always directories/bundles and therefore must
be transported in some type of container.
Merge pull request #1956 from rolandwalker/add_naked_filetypes

Allow naked OTF and TTF files, follow-up on #1860