Add API for writable object property lists (#1206)

Added a new API for writable property lists across all the basic example object types, preparing for the introduction of a Writable_Property_List property in every object in a future BACnet standard revision.

The lists can be used by backup and restore feature to automatically choose the object property values in the backup that can be restored via internal WriteProperty directly from BACnet CreateObject services with  List of Initial Values. 

Updated existing device object examples to include these writable property lists.

src/bacnet/basic/object/schedule.c

@@ -52,6 +52,33 @@ static const int32_t Schedule_Properties_Optional[] = {
 
 static const int32_t Schedule_Properties_Proprietary[] = { -1 };
 
+/* Every object shall have a Writable Property_List property
+   which is a BACnetARRAY of property identifiers,
+   one property identifier for each property within this object
+   that is always writable.  */
+static const int32_t Writable_Properties[] = {
+    /* unordered list of always writable properties */
+    PROP_OUT_OF_SERVICE,
+    PROP_WEEKLY_SCHEDULE,
+    PROP_LIST_OF_OBJECT_PROPERTY_REFERENCES,
+    PROP_EFFECTIVE_PERIOD,
+#if BACNET_EXCEPTION_SCHEDULE_SIZE
+    PROP_EXCEPTION_SCHEDULE,
+#endif
+    -1
+};
+
+/**
+ * Returns the list of required, optional, and proprietary properties.
+ * Used by ReadPropertyMultiple service.
+ *
+ * @param pRequired - pointer to list of int terminated by -1, of
+ * BACnet required properties for this object.
+ * @param pOptional - pointer to list of int terminated by -1, of
+ * BACnet optional properties for this object.
+ * @param pProprietary - pointer to list of int terminated by -1, of
+ * BACnet proprietary properties for this object.
+ */
 void Schedule_Property_Lists(
     const int32_t **pRequired,
     const int32_t **pOptional,
@@ -68,6 +95,20 @@ void Schedule_Property_Lists(
     }
 }
 
+/**
+ * @brief Get the list of writable properties for a Schedule object
+ * @param  object_instance - object-instance number of the object
+ * @param  properties - Pointer to the pointer of writable properties.
+ */
+void Schedule_Writable_Property_List(
+    uint32_t object_instance, const int32_t **properties)
+{
+    (void)object_instance;
+    if (properties) {
+        *properties = Writable_Properties;
+    }
+}
+
 /**
  * @brief Gets an object from the list using an instance number
  * @param  object_instance - object-instance number of the object