Add a pygradethis_setup for setting tutorial options

[nischalshrestha]

We have to have a function that sets up the tutorial options like feedback strings and checking flow, similar to how gradethis does it: https://pkgs.rstudio.com/gradethis/reference/gradethis_setup.html

One other thing we need is to import crucial libs within pygradethis like builtins which we need for returning last value. This could be later incorporated into an adapter class to handle Python exercises via pygradethis.