Make SerializableObject properties const methods

Signed-off-by: MHesham <mhesham.fcis@gmail.com>
Merge branch 'master' of https://github.com/RtsAiResearch/Serialization

Conflicts:
	ObjectSerializer/Include/Serializable.h

Signed-off-by: MHesham <mhesham.fcis@gmail.com>