alias: allow reference through 's#'
We keep the 't#' option, but we hope to be able to deprecate it at some point.
We move to 's#' because it refers to `stack` a more generic concept. than topic.
In addition, this allows to phase out 'b#' that collide with normal hex-node.
syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
^tests/.*\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes
^docs/training/graphs/
^docs/training/html/
^docs/training/index.html
^docs/training/graphviz-images/
^docs/training/img/
^docs/training/output/
^docs/training/pandocfilters/