Introduce Node Role Inheritance

it might be useful to introduce an "inheritance concept" for node roles.
currently one have to apply multiple roles to each node even if they are always used in combination.

example: generic "aem-cms" role plus project-specific "xxx-aem-cms" role.

if "xxx-aem-cms" role would inherit from "aem-cms" it would be sufficient to only specify "xxx-aem-cms" in the environment per node. additionally it reduces the risk to define a parameter value for the wrong role if it is not wholly sure to which it belongs.