"Execute Expect Exception" support

These changes add support for __Expect Exception__ to the basic __Execute__ command in the same manner as is found in the __Execute Procedure__ command. This is a further move towards implementing the request in issue https://github.com/dbfit/dbfit/issues/35.

With the addition of this command it is possible to verify things like integrity constraints without having to create a stored procedure to do so. I might look at adding similar support to update and insert although this patch should provide sufficient functionality to allow update/insert/query violations to be checked without that.

The acceptance tests have only been modified for Derby at this time. It is probably possible to do a generic test of the feature across all databases without expecting a specific error code.