Default file names produced by XmiWriterCasConsumer don't have .xmi extension and can't be read by XmiCollectionReader

If the original source file name is not present in the CAS, the XmiWriterCasConsumer names the output file "doc0","doc1", etc,, with no .xmi extension. The XmiCollectionReader will only read files with .xmi extensions.

This is quite annoying if you're trying to break up a pipeline into two parts, writing and reading XMI files in the middle.