Templated and custom-named classes support and test

[IvanInventor]

Support for template classes, and, as side effect, classes with custom name, different for actual name.
To add template class:

• Replace GDCLASS() macro with GDCLASS_TEMPLATE()

template <class T>
class ExampleTemplated : public Object {
	GDCLASS_TEMPLATE(ExampleTemplated, Object);
};

• For each template instantiation, set name of this class, and optionally explicitly instantiate them

template <>
const char *ExampleTemplated<int>::_template_class_name = "ExampleTemplatedInt";
template class ExampleTemplated<int>;

template <>
const char *ExampleTemplated<float>::_template_class_name = "ExampleTemplatedFloat";
template class ExampleTemplated<float>;

As a side effect after changes, classes with custom name are now also easily created with GDCLASS_NAME(ExampleCustom, Object, "CustomExample"); macro

[dsnopek]

Thanks!

This is an interesting feature. However, one of the design goals of godot-cpp is to provide the same API as is available internally in Godot itself. So, for this to be added to godot-cpp, it'd need to be added first to Godot, so you'd need to propose it there first.