Add dashboard pressure trend arrow

Display/src/app/models/weather/weather-value-type.ts

@@ -0,0 +1,3 @@
+export enum WeatherValueType {
+    Pressure = 'Pressure'
+}

Display/src/app/models/weather/weather-value.ts

@@ -1,4 +1,4 @@
 export class WeatherValue {
-    bucket: string;
-    averageValue: number;
+    timestamp: string;
+    value: number;
 }