Added caching, background refresh, and first widget

- The main dining location information is now cached on download.
   - The freshness of the cache is checked whenever it's loaded, and if the last refreshed date is not today's date then it's dropped and the app refreshes from the API normally.
   - This reduces load times if you open the app multiple times a day. The data won't change during the day, so you can load it the first time and then use the cache the rest of the time.
   - Refreshing via pull to refresh or the refresh button still refreshes the cache from the server.
- Added a background refresh task.
   - TigerDine now registered a background fetch task with the device that will update the location information up to a maximum of 4 times per day. The cache is checked first, so a new request will only be made if the cache is stale.
   - This allows for automatic notification scheduling at times other than when the app is launched. As long as background tasks can run, notifications will be automatically scheduled when necessary.
   - Depending on the timing, this may allow you to never see any load times in TigerDine, since the cache might already be up to date before you use the app for the first time in a day.
- Started adding widgets!
   - TigerDine now offers an hours widget that lets you put the hours for a specified location on your home screen, along with a visual indicator of when that location is open today.
   - The widget automatically feeds off of TigerDine's cache, so hey, no extra network requests required!
   - This widget currently DOES NOT support multi-opening locations like Brick City Cafe or Gracie's. This is still a work in progress.

TigerDine/Views/LocationList.swift

@@ -10,7 +10,6 @@ import SwiftUI
 // This view handles the actual location list, because having it inside ContentView was too complex (both visually and for the
 // type checker too, apparently).
 struct LocationList: View {
-    @Binding var diningLocations: [DiningLocation]
     @Binding var openLocationsFirst: Bool
     @Binding var openLocationsOnly: Bool
     @Binding var searchText: String
@@ -20,7 +19,7 @@ struct LocationList: View {
     // The dining locations need to be sorted before being displayed. Favorites should always be shown first, followed by non-favorites.
     // Afterwards, filters the sorted list based on any current search text and the "open locations only" filtering option.
     private var filteredLocations: [DiningLocation] {
-        var newLocations = diningLocations
+        var newLocations = model.locationsByDay[0]
         // Because "The Commons" should be C for "Commons" and not T for "The".
         func removeThe(_ name: String) -> String {
             let lowercased = name.lowercased()