Removed limitation of vulns to computer parts

Removed: A vulnerability object no longer stores the computer part which is vulnerable.
Fixed: The InfoString-interface now has type-javadoc.
User/Group System

Added: UNIX-like rights system: Users which can be in different groups and always have a primary group (the actual file rights are nyi).
Removed: There're no longer right levels because of the new rights system.
Fixed: Cleaned up the the vulnerability & attack classes.
Fixed: Added some missing toString()-methods.