better error reporting on test failure

Try to recover from errors and collect them all and present them as an
AssertionError if necessary (i.e. fails).
Merge branch 'master' into fixedFormat
introducing FixedFormatAcceptanceTest

FreeFormatAcceptanceTest was refactored and much of its functionality
extracted to AbstractAcceptanceTest.

Both FreeFormat- and FixedFormatAcceptanceTest build upon this new
AbstractAcceptanceTest framework.
code snippets for fixed format acceptance test