New, POSIX Rewrite in New Repo (supports various Linuxes, macOS, and some BSDs)

[coolaj86]

Moving to https://github.com/bnnanet/serviceman-sh
(as we'll ship it as part of our default images for the BNNA project)

After several years of use across hundreds of systems, I've decided to rewrite this in POSIX command language:

• easier to use sudo without losing current ENVs (notably $PATH, $HOME, id -u -n)
• fewer flags and options required
• quicker to hack together simple features and fixes (ex: aliasing other shell commands)
• can release via git tags without build step
• much smaller size
• almost as portable as Go
• but NOT for Windows (I may rewrite that in PowerShell... someday)

Changes to v1.0.0

• openrc support for Alpine, Arch, Gentoo, etc
• Update systemd support
• old --user functionality moved to --on-login (tentative name)
• new --user functionality replaces --username

I'll put the new location in the README once I have the v1.0.0 release. I'll also need to update many cheat sheets.

The README here has been updated, as well as all of the cheat sheets and scripts on Webi.