fix vector copy implied in parseCartesianPosition and parseSphericalPosition

[tomjnixon]

This accepts a vector of nodes:

libadm/src/private/xml_parser.cpp

Line 768 in 3f94a9b

CartesianPosition parseCartesianPosition(std::vector<NodePtr> nodes) {

and it's not moved in here:

libadm/include/adm/private/xml_parser_helper.hpp

Line 254 in 3f94a9b

value = NT(parser(elements));