Write a setup script

[retrixe]

It should support both upgrading Octyne and installing it.

Rough approximation of workflow:

• Detect if Octyne, octynectl and Ecthelion are installed or not.
• If they are:
  • Update the versions of all 3 software.
  • Prompt to install any of them if they are not present.
• Else:
  • Prompt to install what software selection the user wants (download Octyne and octynectl to /usr/local/bin, Ecthelion to /usr/local/share/ecthelion)
• Prompt to setup systemd services for Octyne and Ecthelion (if not already present).
• Warn if services are present in /usr/lib/systemd/system and not /etc/systemd/system.

Additional features:

• Have flags --setup=octyne,ecthelion,octynectl, --no-systemd, --version=stable/git, --update-only, --install-only