Fixed problem where fields contained shared values by
performing a shallow copy on all fields during Record instantiation.
That way, each record has its own copy of the field instances, rather
than the shared class-wide instance provided by the definition.
Found a fairly difficult bug involved with Field instances
being shared across Records. The issue is that Field instances
are static. I either need to implement a way to instantiate
copies of all the Fields per-record, or write a wrapping
interface which provides a unique value store on a per-Record
basis.
