Sharing describe roles: resolve role inheritance

This pull request improves the sharing "describe roles" view to resolve role inheritance and include those action groups and transitions.

I've refactored out the role inheritance helpers into utils functions and tried to make clearer what they actually do :wink: 

I've also extended the english role parsing to support role inheritance statements without an article, which allows to remove "an" in this example:
-  An editor can perform the same actions as ~~an~~ Everyone.
where `Everyone` is `Anonymous`..

@maethu @deiferni