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/lighting.h

@@ -86,6 +86,9 @@ typedef struct BACnetColorCommand {
 #define BACNET_COLOR_STEP_INCREMENT_MIN 1ul
 #define BACNET_COLOR_STEP_INCREMENT_MAX 30000ul
 
+#define BACNET_COLOR_TEMPERATURE_MIN 1000ul
+#define BACNET_COLOR_TEMPERATURE_MAX 30000ul
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
@@ -140,6 +143,20 @@ extern "C" {
     bool xy_color_same(
         BACNET_XY_COLOR *value1,
         BACNET_XY_COLOR *value2);
+    BACNET_STACK_EXPORT
+    void xy_color_set(
+        BACNET_XY_COLOR *dst,
+        float x,
+        float y);
+    BACNET_STACK_EXPORT
+    int xy_color_to_ascii(
+        const BACNET_XY_COLOR *value,
+        char *buf,
+        size_t buf_size);
+    BACNET_STACK_EXPORT
+    bool xy_color_from_ascii(
+        BACNET_XY_COLOR *value,
+        const char *arg);
 
     BACNET_STACK_EXPORT
     int color_command_encode(