This is by Lars Toenning <dev@ltoenning.de>, Roman Ludwicki <romek21@op.pl> and
SDeAstis <salvatore.deastis@gmail.com>, in 2021 Hackathon.
SGPropertyNode::getStringValue() now returns std::string by value instead of
const char* pointer into SGPropertyNode's internal data.
Patched up various call sites to use new API.
Remove SGPropertyNode::getName() and use SGPropertyNode::getNameString()
everywhere.
Lars Toenning
dd09e5f466