Guid is always not nullable

[lukaszkierepka]

query-first/QueryFirst/Providers/SqlClient.cs

Line 241 in fe2b66b

return "Guid";

Guid is a struct so it should be

return nullable ? "Guid?" : "Guid";

EDIT
Change in SqlClient is not required I think. Change in System2Alias.cs is sufficient.

[lukaszkierepka]

query-first/QueryFirst/SchemaFetching/TypeMappings/System2Alias.cs

Line 27 in 54d3b1e

{"System.UInt16","ushort" }

to make it work it should be added here as well.
And the same goes for System.DateTime