skip vim's transient files when including whole dir trees via manifests

[dlowe]

This adds logic to skip vim's .swp transient files, same as the emacs .# ones.

Also fixes the emacs test (the "nested" directory only gets slurped if it's named with a trailing slash in the manifest!)

Also switches from (filter (and (not x) (not y) (not z))) to (remove (or x y z)).