Added hasPermission function to the auth service to check for permissions.

Added: Bill Type selection
Fix: Add product would add to old kots if product was added earlier

bookie/src/app/auth/auth.service.ts

@@ -70,4 +70,8 @@ export class AuthService {
       );
   }
 
+  hasPermission(permission: string) : boolean {
+    return this.user !== undefined && this.user.isAuthenticated && this.user.perms.indexOf(permission) !== -1;
+  }
+
 }