Modify Table class so that uploadfs is respected when uploads_in_blob is set to True

This patch addresses an issue where a database adapter has ```uploads_in_blob = True``` (e.g. ```HerokuPostgresAdapter```) and an upload field has ```uploadfs``` specified.  Currently, the specified ```uploadfs``` is not used, and the data is stored as a blob in the database.  The solution presented here checks whether ```uploadfs``` is set before setting the file to be stored as a blob.