Feature/raspberry pi blinkt color objects (#503)

* fixed BACnetXYcolor and BACnetColorCommand encode and decoding and improved unit test coverage. Refactored BACnetXYcolor to/from ascii into lighting module.

* added to the color, color temperature, and lighting output objects a fade/ramp/step engine.  Added color and color command coercion into the channel object and enabled color temperature object coercion.  Added CreateObject and DeleteObject service handling to the color, color temperature, lighting output, and channel objects.

* added blinkt demo app for Raspberry Pi [WIP]

* updated gitignore to simplify handling of apps folder contents

* fixed piface demo build

* added RaspiOS to pipeline for piface and blinkt! demo builds

* added device object timer function for child object types into example Device object.  Refactored device object to increment database revision for create or delete object services.   Refactored example app/server to use mstimer library and device child object timers.

---------

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/basic/object/device.h

@@ -142,6 +142,14 @@ typedef void (
     *object_intrinsic_reporting_function) (
     uint32_t object_instance);
 
+/**
+ * @brief Updates the object with the elapsed milliseconds
+ * @param  object_instance - object-instance number of the object
+ * @param milliseconds - number of milliseconds elapsed
+ */
+typedef void (
+    *object_timer_function) (
+    uint32_t object_instance, uint16_t milliseconds);
 
 /** Defines the group of object helper functions for any supported Object.
  * @ingroup ObjHelpers
@@ -172,6 +180,7 @@ typedef struct object_functions {
     list_element_function Object_Remove_List_Element;
     create_object_function Object_Create;
     delete_object_function Object_Delete;
+    object_timer_function Object_Timer;
 } object_functions_t;
 
 /* String Lengths - excluding any nul terminator */
@@ -233,6 +242,10 @@ extern "C" {
     void Device_Init(
         object_functions_t * object_table);
 
+    BACNET_STACK_EXPORT
+    void Device_Timer(
+        uint16_t milliseconds);
+
     BACNET_STACK_EXPORT
     bool Device_Reinitialize(
         BACNET_REINITIALIZE_DEVICE_DATA * rd_data);