Fix multiple low priority issues

closes #12, closes #80, closes #95, closes #96, closes #99

- Issue #12: Set tp_new to NULL for GridPoint and GridPointState to prevent instantiation from Python
- Issue #80: Renamed Caption.size to Caption.font_size for semantic clarity
- Issue #95: Fixed UICollection repr to show actual derived types instead of generic UIDrawable
- Issue #96: Added extend() method to UICollection for API consistency with UIEntityCollection
- Issue #99: Exposed read-only properties for Texture (sprite_width, sprite_height, sheet_width, sheet_height, sprite_count, source) and Font (family, source)

All issues have corresponding tests that verify the fixes work correctly.

src/PyTexture.h

@@ -26,6 +26,16 @@ public:
     static Py_hash_t hash(PyObject*);
     static int init(PyTextureObject*, PyObject*, PyObject*);
     static PyObject* pynew(PyTypeObject* type, PyObject* args=NULL, PyObject* kwds=NULL);
+    
+    // Getters for properties
+    static PyObject* get_sprite_width(PyTextureObject* self, void* closure);
+    static PyObject* get_sprite_height(PyTextureObject* self, void* closure);
+    static PyObject* get_sheet_width(PyTextureObject* self, void* closure);
+    static PyObject* get_sheet_height(PyTextureObject* self, void* closure);
+    static PyObject* get_sprite_count(PyTextureObject* self, void* closure);
+    static PyObject* get_source(PyTextureObject* self, void* closure);
+    
+    static PyGetSetDef getsetters[];
 };
 
 namespace mcrfpydef {
@@ -38,6 +48,7 @@ namespace mcrfpydef {
         .tp_hash = PyTexture::hash,
         .tp_flags = Py_TPFLAGS_DEFAULT,
         .tp_doc = PyDoc_STR("SFML Texture Object"),
+        .tp_getset = PyTexture::getsetters,
         //.tp_base = &PyBaseObject_Type,
         .tp_init = (initproc)PyTexture::init,
         .tp_new = PyType_GenericNew, //PyTexture::pynew,