Convert authnet transaction id data type to String
Merge pull request #169 from CruGlobal/mod/convert-transaction-data-type

Convert Authorize.Net transaction id data type to String
In prepration for actual usage of the tool, don't allow the authnet code to fall back to the test account ID for processing payments
Make sure before attmepting to process a `Payment`, that the `ConferenceCostsEntity` has the appropriate authnet information.
Removing redundant code at @hlbraddock's request