Changed cache key for regenerating the configuration it if there are setup issues

--HG--
branch : dev

src/Orchard/Data/SessionConfigurationCache.cs

@@ -105,6 +105,9 @@ namespace Orchard.Data {
         private Hash ComputeHash() {
             var hash = new Hash();
 
+            hash.AddString(_shellSettings.DataProvider);
+            hash.AddString(_shellSettings.DataTablePrefix);
+            hash.AddString(_shellSettings.DataConnectionString);
             hash.AddString(_shellSettings.Name);
 
             // We need to hash the assemnly names, record names and property names

src/Orchard/Utility/Hash.cs

@@ -12,6 +12,8 @@ namespace Orchard.Utility {
         public string Value { get { return _hash.ToString(); } }
 
         public void AddString(string value) {
+            if ( string.IsNullOrEmpty(value) )
+                return;
             _hash += value.GetHashCode();
         }