`$param isa Class`, `$param does Role` and `$param type Type` traits

[schwern]

As discussed on p5-syntax, Thing $param is ambiguous because one doesn't know if Thing is supposed to be a type or a class or a role and this can have consequences having to do with the order things are loaded.

Add the traits isa, does and type to unambiguously check that the parameter isa class, does a role or is of the type, respectively. There can be multiple checks on one parameter.