Added basic timer object, internal state machine, and unit tests (#1123)

* Added basic timer object, internal state machine, and unit tests

* Added BACnetTimerStateChangeValue encode, decode, parse, print, and diff with unit tests

* Changed handler of add/remove list element to check if the property is a BACnetLIST

* Added BACnetLIST utility for handling WriteProperty to a list.

* Fixed outlier ReadProperty object handlers to return zero when the RP parameter is NULL.

test/bacnet/bacapp/src/main.c

@@ -72,7 +72,15 @@ static const BACNET_APPLICATION_TAG tag_list[] = {
     /* BACnetShedLevel */
     BACNET_APPLICATION_TAG_SHED_LEVEL,
     /* BACnetAccessRule */
-    BACNET_APPLICATION_TAG_ACCESS_RULE
+    BACNET_APPLICATION_TAG_ACCESS_RULE,
+    /* BACnetChannelValue */
+    BACNET_APPLICATION_TAG_CHANNEL_VALUE,
+    /* BACnetLogRecord */
+    BACNET_APPLICATION_TAG_LOG_RECORD,
+    /* BACnetTimerChangeValue */
+    BACNET_APPLICATION_TAG_TIMER_VALUE,
+    /* no-value - context tagged null */
+    BACNET_APPLICATION_TAG_NO_VALUE
 };
 
 /**