UX: Move acorn system related commands to a sub command

[hikhvar]

Commands like arcorn install, acorn uninstall, acorn info are in the top level of the acorn sub commands. For me it was hard to figure out, which commands are intended for the developer and which should be used by persons who operate the acorn installation. I would propose to move the install, uninstall and info subcommands into a subcommand called system. So

acorn install becomes acorn system install acorn uninstall becomes acorn system uninstall acorn info becomes acorn system info.

I think this makes it more clear what the commands do. Moreover, it's more clear what the difference between e.g. acorn uninstall and acorn rm is.

[cjellick]

Will bring up for discussion and report back. =

[cjellick]

Need to discuss with the team to see if we want to do this.

[cjellick]

This isn't likely to change