ORM test Fail with nullable<TDateTime>

[Friedrich Westermann]

The TSession-Tests with TCustomer_Orders are failing with EInvalidCast. It seems the Cast from Nullable<TDatetime> to System.TDateTime are broken. But I don't see the real problem. The Casts are registered in Spring.ValueConverters.

[Stefan Glienke]

use ToType instead of AsType to use custom type conversion (fixes #279)

→ <<cset a03b6908ee3f>>