Shell Check fixes

[stealthybox]

• Greatly reduce shellcheck issues to a smaller list
• Reduce globbing errors by wrapping everything in d-quotes and braces: "${var}" / "$(cmd)" vs $var / $(cmd)
• Wrap footloose in do_footloose() to fix PATH's with spaces to not crashing the script
• Remove unneeded echo's
• Fix broken reference to $arg that causes crash
• Expose sudo as an overrideable ENV var: sudo="" ./setup.sh