fix: multiple usage of app header (#48)

Remove multiple usage of app header component and use the shell component
to route with shell, loading the header only once initially.

Fixes #47

src/app/accounting/accounting-routing.module.ts

@@ -1,10 +1,13 @@
 import { NgModule } from '@angular/core';
 import { Routes, RouterModule } from '@angular/router';
 
+import { Route, extract } from '@app/core';
 import { AccountingComponent } from './accounting.component';
 
 const routes: Routes = [
-  { path: 'accounting', component: AccountingComponent},
+  Route.withShell([
+    { path: 'accounting', component: AccountingComponent}
+  ])
 ];
 
 @NgModule({

src/app/accounting/accounting.component.html

@@ -1,4 +1,3 @@
-<app-header> </app-header>
 <div class="fluid-container">
  <div class="container">
    <div class="card-body">
@@ -47,4 +46,4 @@
     </div>
    </div>
   </div>
-</div> 
+</div>