* Added ListElement service callback for storing data.
* Added Audit Log and Time Value objects to basic device.
* Added Audit Log object to Makefile and CMake builds.
* 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.
* Converted device object test to use common read-write property test. Extended the basic BACnet device object example API.
* Created BACnet/IP and COV test mocks to enable device object testing with less dependencies.
Steve Karg