Squashed: grid-entity-integration partial features for 7DRL 2025 deployment

This squash commit includes changes from April 21st through 28th, 2024, and the past 3 days of work at 7DRL.
Rather than resume my feature branch work, I made minor changes to safe the C++ functionality and wrote workarounds in Python.

I'm very likely to delete this commit from history by rolling master back to the previous commit, and squash merging a finished feature branch.

src/PyVector.h

@@ -1,6 +1,7 @@
 #pragma once
 #include "Common.h"
 #include "Python.h"
+#include "McRFPy_API.h"
 
 typedef struct {
     PyObject_HEAD
@@ -22,6 +23,7 @@ public:
     static PyObject* pynew(PyTypeObject* type, PyObject* args=NULL, PyObject* kwds=NULL);
     static PyObject* get_member(PyObject*, void*);
     static int set_member(PyObject*, PyObject*, void*);
+    static PyVectorObject* from_arg(PyObject*);
     
     static PyGetSetDef getsetters[];
 };