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.

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

src/bacnet/wp.c

@@ -66,7 +66,6 @@ int wp_encode_apdu(
 {
     int apdu_len = 0; /* total length of the apdu, return value */
     int len = 0; /* total length of the apdu, return value */
-    int imax = 0; /* maximum application data length */
 
     if (!wpdata) {
         return BACNET_STATUS_ERROR;
@@ -155,8 +154,6 @@ int wp_decode_service_request(
 {
     int len = 0;
     int apdu_len = 0;
-    int tag_len = 0;
-    uint8_t tag_number = 0;
     uint32_t instance = 0;
     BACNET_OBJECT_TYPE type = OBJECT_NONE; /* for decoding */
     uint32_t property = 0; /* for decoding */