#2 query operations for role hierarchy

[Jens Lehmann]

The reasoning service should support the following methods to query the role hierarchy:

- retrieve subroles of a given role
- retrieve superroles of a given role
- get most general roles
- get most special roles

[Jens Lehmann]

Logged In: YES
user_id=1620101
Originator: YES

All these methods are now implemented.