Feature/clob file reference bug test

Test case for the related PR https://github.com/liquibase/liquibase/pull/221

I've included the test in a separate PR as it takes a more integrative approach than the existing test cases using a in memory DB (for which I had to add a new dependency to the project) instead of mock objects.

Note that this contains only the test (which will fail without the fix of PR 221).