Store-centric UI (#3091)

* Update layout structure and header

* Implement store selector

* Simplify homepage

* Update layout

* Use dropdown for store selector

* Hide global nav in store context

* Horizontal section nav

* Remove outer section and container from content views

* Update nav

* Set store context for invoice and payment request lists

* Test fixes

* Persist menu collapse state on client-side

* MainNav as view component

* Update app routes to incorporate store context

* Test fixes

* Display ticker for altcoins build only

* Plugins nav

* Incorporate category for active page as well

* Update invoice icon

* Add apps list to nav

* Add store context to app type controllers

* Incorporate id for active page as well

* Test fixes

* AppsController cleanup

* Nav: Display only apps for the current store

* Remove leftover from merge

* Nav styles optimization

* Left-align content container

* Increase sidebar padding on desktop

* Use min-width for store selector menu

* Store settings nav update

* Update app and payment request routes

* Test fixes

* Refactor MainNav component to use StoresController

* Set store context for invoice actions

* Cleanups

* Remove CurrentStore checks

The response will be "Access denied" in case the CookieAuthorizationHandler cannot resolve the store.

* Remove unnecessary store context setters

* Test fix

BTCPayServer/Components/StoreSelector/StoreSelectorViewModel.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace BTCPayServer.Components.StoreSelector
+{
+    public class StoreSelectorViewModel
+    {
+        public List<SelectListItem> Options { get; set; }
+        public string CurrentStoreId { get; set; }
+        public string CurrentDisplayName { get; set; }
+    }
+}