Add transition and delay timers to models.

* Remove level server setDelta() callback as it is unnecessary.

* Add target value and remaining time to status messages.

examples/mesh/basic_on_off_level_server/main/main.cpp

@@ -22,7 +22,7 @@ class onOffSrvModelCallbacks : public NimBLEMeshModelCallbacks {
     }
 
     uint8_t getOnOff() {
-        printf("on/off get val %d", onOffVal);
+        printf("on/off get val %d\n", onOffVal);
         return onOffVal;
     }
 };
@@ -33,11 +33,6 @@ class levelSrvModelCallbacks : public NimBLEMeshModelCallbacks {
         levelVal = val;
     }
 
-    void setDelta(int16_t val) {
-        printf("Level set delta %d\n", val);
-        levelVal += val;
-    }
-
     int16_t getLevel() {
         printf("Level get val %d\n", levelVal);
         return levelVal;