Marshal out

This completely replaces the use of Marshal in rOCCI-core specs with YAML

Key changes:
* "expected" objects are stored in a plain text format (YAML)
* Objects are not restored for comparison, but the other way round. I.e., objects one wishes to compare are stored in YAML and then the YAML files are compared
* Two approaches to YAML comparison were tested. In the end, whole YAML lines of text are compared.

I think this is ready for merge.