*: unify version numbers

[asymmetric]

Move away from semantic versioning, and simplify release process.

The rationale is that we get very little benefit by using SemVer, because backwards compatibility isn't really applicable to us: there is no state, and users just want to be on the latest. It could be argued we don't need versions, and could just use a commit hash instead. I think versions help by making it clear how far behind one is to latest.

NOTE: Only seth cause it's a draft, but the same would apply for other tools.

The version number patching happening in Nix means this doesn't support make-based builds, /cc @rainbreak.

[asymmetric]

This should probably be postInstall and the current postInstall should be postFixup.

[rainbreak]

Would be nice if the --version output both the version number and the commit hash. This would help with 1) easy checkout and 2) disambiguation if I build locally from an unbumped development version.

[asymmetric]

Sidenote: I think --version should actually be version, since it's not a flag to another command but a command in itself, IMO.

Unless one sees it as a flag to seth. But I don't see it that way ;)

But this should probably be a larger discussion, since it applies to many other commands (namely, the conversion ones).

[rainbreak]

I think --version is more expected from other cli tools, so it should at least alias to version (e.g. git allows both). Also we have seth --to-wei etc. as commands rather than flags.