feat: different variable scope

[Jan0660]

Allow variables to have a scope specified like $global:profile_path.

• global for variables in the global scope
• current for the current scope, e.g. { $h = 1; { $local:h =2; print $local:h; } print $h; } would result in 2 and 1 being printed
• (RCaron.Shell) env for setting and getting environment variables