Determine value of runtime construction and modifcation of classes

[stevehalliwell]

And if valued, propose draft.

The VM constructs class objects via opcodes during execution there is little in the way of allowing a library to run the same vm operations and letting the user manually create or modify classes themselves.

[stevehalliwell]

This would include classof.

[stevehalliwell]

Using this to do a similar thing to extension methods might be cool, but it seems like a feature that only makes sense in larger, system languages.

[stevehalliwell]

Re #90 being able to extend a class without changing it kicks in here, the assert fluent case also requires this to function across the from script classes and natively defined classes.

[stevehalliwell]

This would mesh nicely with #146