Add XML failure cases invalid by the schema

[mristin]

We checked so far only that the valid XML files are correctly accepted by the XML validator. This patch introduces a suite of XML files which are invalid according to the schema.

The error messages are stored as-are in the test resources so that we can verify not only the acceptance/rejection logic, but the content of the validation records as well.

[CLAassistant]

All committers have signed the CLA.