Custom Up and down roles inheritence

[Exelord]

Some roles have to have downgraded level after down inheritance.
Eg.
When you grant user to a resource A as Owner and then create a child for resource A as resource B you want to inherit role from A to B but with downgraded level eg. as manager.

In fact in resource A user will be owner and in resource B will be manager

TODO:

• create a column named downgraded_role and set as nil by default
• rework on role_for method to obtain a correct downgraded role if exist
• write tests

And think about upgraded_role... Maybe there will be also some use cases.

[Exelord]

Done! :) (ONLY DOWNGRADED_ROLE)