Added a test that checks that the static resources returned by the
server have content that matches their cacheid. This test currently
fails because some binary resources (e.g. png images) are garbled by the
dos2unix conversion.

... so that all resources have extensions and can be automatically
categorized as binary or text based on extension (coming next).

Now if a static resource of a new type is added the build will
fail unless the list of known file type extensions is updated.