gdown/gup: add next/previous alias Up and down refer to the customary order in log output rather than concepts; as such, it may be confusing to the user. I for one found them suprising -- they just didn't fit with my mental model. Previous and next, however, imply a clear parent/child relationship. We attroduce the new name as aliases for now.

syntax: re
/figures/[^/]+\.png$
^docs/build/
^docs/html/
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$