Refactor Error type to show more details

[tazz4843]

The Error type as it stands in Scripty shows no information about where it was created. We can solve this rather easily by making a wrapper struct around the enum and switching from creating enum variants to functions, in which (for example) a function to create a backtrace is automatically called. It'd be nice if we were able to implement the full API surface of std::error::Error.