Fix exceptions (more explicit)

src/Umbraco.Core/Cache/HttpRuntimeCacheProvider.cs

@@ -154,7 +154,7 @@ namespace Umbraco.Core.Cache
 
             value = result.Value; // will not throw (safe lazy)
             var eh = value as ExceptionHolder;
-            if (eh != null) throw eh.Exception; // throw once!
+            if (eh != null) throw new Exception("Exception while creating a value.", eh.Exception); // throw once!
             return value;
         }
 

src/Umbraco.Core/Services/EntityService.cs

@@ -132,7 +132,7 @@ namespace Umbraco.Core.Services
                         case UmbracoObjectTypes.ROOT:
                         case UmbracoObjectTypes.Unknown:
                         default:
-                            throw new NotSupportedException();
+                            throw new NotSupportedException("Unsupported object type (" + umbracoObjectType + ").");
                     }
                 }
             });