Product Group renamed to Menu Category

Extracted Product Group -> Group_type to a a new object called Sale Category.
Moved tax from product to Sale Category for uniform taxes on types of sales.

bookie/src/app/menu-category/menu-category-resolver.service.spec.ts

@@ -0,0 +1,14 @@
+import { inject, TestBed } from '@angular/core/testing';
+import { MenuCategoryResolver } from './menu-category-resolver.service';
+
+describe('MenuCategoryResolver', () => {
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      providers: [MenuCategoryResolver]
+    });
+  });
+
+  it('should be created', inject([MenuCategoryResolver], (service: MenuCategoryResolver) => {
+    expect(service).toBeTruthy();
+  }));
+});