gcli command auto completion and arm64 build

• Extra command completion added which takes a --shell argument to generate a completions script for a specified shell.
• Adapted the Linux (amd64) build to:
  • generate the gcli-completion.bash, gcli-completion.zsh, gcli-completion.fish, gcli-completion.ps1 completion scripts
  • add the bash, zsh and fish completion scripts in the .deb package
• Added the ARM64 build generating a binary and a .deb package that also include those completion scripts.
• Includes fix for #50 (closed)