CHANGE: Rename product_* config options to release_* for consistency with productmd.
ACTION: Rename product_name, product_short, product_version, product_is_layered to release_* in config files.
Rename //variant/product to //variant/release in variants XML.
Previous test data was insufficient for proper testing.
Test compose runs and depsolving tests require precisely
set NVRs, dependencies, sub-packages, etc.
Using rpmfluff for these would be an overkill, it's better
to create RPMs directly from specs.
