ADDED:
```AMExporter::krID``` to add 'ID' (```scan->id()```)keyword to the
kewword replacer in AMExporter
MODIFIED:
change AMExporter::krID to AMExporter::krSerial, and associate keyword
to 'serial', to be consistent with GSE nomenclature.
Merge pull request #906 from acquaman/Issue905

Checked over and tested. Works on my Mac using the SGMAcquaman application.