utility: add a template alias that will be used in evolve msgs This template use stack alias s# instead of rev number in messages printed when we run `hg evolve`. For example, this template's msgs will look like this: move:[s3] add aaa atop:[s2] add bbb move:[s4] add ccc I will be using this template in upcoming patches.

topic: add topicidx template keyword This keyword will be useful where we want to see the index of the changeset in the stack when we run `hg stack`.

changelog: fix version number