Render the routings based on permissions.

As #2096719: Access denied on link to Structure on '/admin' when having only 'access administration pages' fails I wanted to render the _permission provided by the system module.

This code is now available on admin/config/system/graphapi/modules/routing by graphapi_devel

It needs more features:
- select a module to graph instead of all.
- use _access instead of _permission

How should we visualize these?