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.

src/bacnet/config.h

@@ -244,6 +244,8 @@
     defined(BACAPP_SHED_LEVEL) || \
     defined(BACAPP_ACCESS_RULE) || \
     defined(BACAPP_CHANNEL_VALUE) || \
+    defined(BACAPP_TIMER_VALUE) || \
+    defined(BACAPP_NO_VALUE) || \
     defined(BACAPP_LOG_RECORD) || \
     defined(BACAPP_SECURE_CONNECT) || \
     defined(BACAPP_TYPES_EXTRA))
@@ -294,6 +296,8 @@
 #define BACAPP_SHED_LEVEL
 #define BACAPP_ACCESS_RULE
 #define BACAPP_CHANNEL_VALUE
+#define BACAPP_TIMER_VALUE
+#define BACAPP_NO_VALUE
 #define BACAPP_LOG_RECORD
 #define BACAPP_SECURE_CONNECT
 #endif
@@ -321,6 +325,8 @@
     defined(BACAPP_SHED_LEVEL) || \
     defined(BACAPP_ACCESS_RULE) || \
     defined(BACAPP_CHANNEL_VALUE) || \
+    defined(BACAPP_TIMER_VALUE) || \
+    defined(BACAPP_NO_VALUE) || \
     defined(BACAPP_LOG_RECORD)
 #define BACAPP_COMPLEX_TYPES
 #endif