Improve database properties view: (#501)

- Compatibility Level should be a numerical value. In using `enum.ToString()` the result was `Version140` instead of `140`
- Backup date should be sensible if never backed up. Added a simple check that states it was never backed up if the backup date is before 1900.

src/Microsoft.SqlTools.ServiceLayer/Admin/Database/DatabaseTaskHelper.cs

@@ -18,6 +18,8 @@ namespace Microsoft.SqlTools.ServiceLayer.Admin
 {
     public class DatabaseTaskHelper: IDisposable
     {
+        private static DateTime minBackupDate = new DateTime(1900, 1, 1);
+
         private DatabasePrototype prototype;
 
         private XmlDocument document;
@@ -109,9 +111,9 @@ namespace Microsoft.SqlTools.ServiceLayer.Admin
             databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.RecoveryModel, prototype.RecoveryModel.ToString());
             databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.IsSystemDB, prototype.IsSystemDB.ToString());
             databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.AnsiNulls, prototype.AnsiNulls.ToString());
-            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.CompatibilityLevel, prototype.DatabaseCompatibilityLevel.ToString());
-            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.LastBackupDate, prototype.LastBackupDate.ToString());
-            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.LastLogBackupDate, prototype.LastLogBackupDate.ToString());
+            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.CompatibilityLevel, (int)prototype.DatabaseCompatibilityLevel);
+            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.LastBackupDate, GetBackupDate(prototype.LastBackupDate));
+            databaseInfo.Options.Add(AdminServicesProviderOptionsHelper.LastLogBackupDate, GetBackupDate(prototype.LastLogBackupDate));
 
             databaseInfo.Options.Add(
                 AdminServicesProviderOptionsHelper.FileGroups + "Count", 
@@ -151,6 +153,16 @@ namespace Microsoft.SqlTools.ServiceLayer.Admin
             return databaseInfo;
         }
 
+        private static string GetBackupDate(DateTime backupDate)
+        {
+            if (backupDate == null
+                || backupDate < minBackupDate)
+            {
+                return SR.NeverBackedUp;
+            }
+            return backupDate.ToString();
+        }
+
         private static T GetValueOrDefault<T>(string key, Dictionary<string, object> map, T defaultValue) 
         {
             if (map != null && map.ContainsKey(key))

src/Microsoft.SqlTools.ServiceLayer/Localization/sr.strings

@@ -802,6 +802,7 @@ general_containmentType_None = None
 general_containmentType_Partial = Partial
 filegroups_filestreamFiles = FILESTREAM Files
 prototype_file_noApplicableFileGroup = No Applicable Filegroup
+NeverBackedUp = Never
 
 ############################################################################
 # Backup Service