re #15289

The converted text is stored in separate .rst files in the docs directory.
Refs #9562

and added unit test to test ok

In the end it wasn't correct to change from using the workspace name,
but I made a couple of improvements - use the InstrumentValidator and
improve the test and make it more efficient.

1. Throw an exception if user specifies the name of the output table workspace
same as input matrix workspace.
2. Change the property for output correction file to optional save.