Adding an IsVoid function to Atom::TCore
1. Throwing an error when trying to de-reference a key that does not exist (when it's not being read as an optional of that type)
2. Using IsVoid to reduce the instruction count when reading from the database as an optional.
Merge pull request #194 from jmlvanre/deref-non-key

Throw when de-referencing a key that does not exist