added last downtime log (closes #55)

added uptime statistics (closes #56)
added german translations (closes #57)

src/app/_service/storage.service.ts

@@ -0,0 +1,30 @@
+import {Inject, Injectable, PLATFORM_ID} from '@angular/core';
+import {isPlatformBrowser} from '@angular/common';
+
+@Injectable({
+  providedIn: 'root'
+})
+export class StorageService {
+  constructor(@Inject(PLATFORM_ID) private platformId: Object) {
+  }
+
+  getValue(key: string): any {
+    if (!isPlatformBrowser(this.platformId)) {
+      return null;
+    }
+    try {
+      return JSON.parse(localStorage.getItem(key));
+    } catch (e) {
+      return null;
+    }
+  }
+
+  setValue(key: string, value: any): void {
+    if (isPlatformBrowser(this.platformId)) {
+      try {
+        localStorage.setItem(key, JSON.stringify(value));
+      } catch (e) {
+      }
+    }
+  }
+}