Added icons for iOS. Broke out data access into repositories. Added syncing service.

src/App/Repositories/FolderApiRepository.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Bit.App.Abstractions;
+using Bit.App.Models.Api;
+using Newtonsoft.Json;
+
+namespace Bit.App.Repositories
+{
+    public class FolderApiRepository : ApiRepository<FolderRequest, FolderResponse, string>, IFolderApiRepository
+    {
+        protected override string ApiRoute => "folders";
+
+        public virtual async Task<ApiResult<ListResponse<FolderResponse>>> GetByRevisionDateAsync(DateTime since)
+        {
+            var requestMessage = new TokenHttpRequestMessage()
+            {
+                Method = HttpMethod.Get,
+                RequestUri = new Uri(Client.BaseAddress, string.Concat(ApiRoute, "?since=", since)),
+            };
+
+            var response = await Client.SendAsync(requestMessage);
+            if(!response.IsSuccessStatusCode)
+            {
+                return await HandleErrorAsync<ListResponse<FolderResponse>>(response);
+            }
+
+            var responseContent = await response.Content.ReadAsStringAsync();
+            var responseObj = JsonConvert.DeserializeObject<ListResponse<FolderResponse>>(responseContent);
+            return ApiResult<ListResponse<FolderResponse>>.Success(responseObj, response.StatusCode);
+        }
+    }
+}