IDProperty python module update

- add support for IDProp array slicing, but not resizing.
- rename array attribute type to typecode and use chars 'f', 'd', 'i' which match pythons array module. (was using int's which only have a meaning internally).
- rename function 'convert_to_pyobject' to 'to_dict' and 'to_list' for IDProp group and array types respectively.
- remove 'len' array attribute, calling len(array) is fine.

source/blender/python/generic/IDProp.h

@@ -37,14 +37,15 @@ struct BPy_IDGroup_Iter;
 typedef struct BPy_IDProperty {
 	PyObject_VAR_HEAD
 	struct ID *id;
-	struct IDProperty *prop, *parent;
+	struct IDProperty *prop; /* must be second member */
+	struct IDProperty *parent;
 	PyObject *data_wrap;
 } BPy_IDProperty;
 
 typedef struct BPy_IDArray {
 	PyObject_VAR_HEAD
 	struct ID *id;
-	struct IDProperty *prop;
+	struct IDProperty *prop;  /* must be second member */
 } BPy_IDArray;
 
 typedef struct BPy_IDGroup_Iter {