Fix segfaulting in 64x arch

- Fixe MojVector::release
- Make MojObject polymorphic, added compiller-safe type casts, remove dangerous reinterperet_cast

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <msditanov@luxoft.com>

Change-Id: I5ebccfb32a17c68f637f2709e668242323030bc1