Added the ability to refresh out backend metadata (#2078)

We now can refresh the Plex Metadata in our database. For example if the Plex Agent for TV Shows is TheMovieDb, we will use that and populate the IMDB Id and TheTvDb Id's so we can accuratly match and search things.

Also improved the Job settings page so we can Test CRON's and we also validate them.

src/Ombi.Store/Repository/IRepository.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Query;
 using Ombi.Store.Entities;
 
@@ -24,5 +25,6 @@ namespace Ombi.Store.Repository
             where TEntity : class;
 
         Task ExecuteSql(string sql);
+        DbSet<T> _db { get; }
     }
 }