web-ui: Add config file with first value currentCurrency

Add config file in app/
Use config value currentCurrency in explorerCurrency pipe

web-ui/src/app/config.ts

@@ -0,0 +1,3 @@
+export class Config {
+    static currentCurrency = 'XSN';
+}

web-ui/src/app/pipes/explorer-currency.pipe.ts

@@ -1,10 +1,11 @@
 import { Pipe, PipeTransform } from '@angular/core';
+import { Config } from '../config';
 
 @Pipe({
   name: 'explorerCurrency'
 })
 export class ExplorerCurrencyPipe implements PipeTransform {
   transform(currency: any): string {
-    return `${ currency } XSN`;
+    return `${ currency } ${ Config.currentCurrency }`;
   }
 }