Support new data type mapping for sqlite

[wangzq]

I was trying to use this to read firefox places.sqlite database and noticed it is not showing the title or url fields, which are using "longvarchar" data type; further investigation shows that this is because SQLProvider is relying on System.Data.Sqlite SQLiteConnection.GetSchema("DataTypes"), which in turn is just a xml file in its resource that defines some common data type mappings.

Instead of adding the data type mapping in System.Data.SQLite, I think supporting additional data type mapping when constructing the SqlDataProvider should be a better approach.

Thanks