SVector: from/to string conversion is now managing empty vectors and empty streams (that happens for vector<SVector<T>>)
SVector: from/to string conversion is now managing empty vectors and empty streams (that happens for vector<SVector<T>>)

Former-commit-id: 4795fdab187c3d32e3ae0ea4b07d60f30265094e
hdeling/sofa,hdeling/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,Anatoscope/sofa,Anatoscope/sofa,hdeling/sofa