[Feature] Add function to bring more fun in console

[DerpyNewbie]

Add new function syntax for even more fun in this console
function <func_name>([vars]){ <commands> [return [value];] }

Which can be called at runtime by
<func_name>([vars])

Which may return value like so
echo <func_name>([vars])

The implementation should allow this example command:

function return_empty_function() {
  echo "return empty func called";
  return;
}

function return_value_func() {
  echo "return value func called";
  return "a value";
}

function print_var_func(var1) {
  echo var1;
  return;
}

return_empty_function();
print_var_func(return_value_func());

Which results in:

return empty func called
return value func called
a value