Root Overhaul & File Rights

Added: There's no longer something like a "right override"; The superuser is now marked by his name "root".
Added: File rights do now partly work! In the next commit, we'll add file right checks for programs.
Functional Right System!

Added: Static methods for checking rights.
Added: Methods for accessing files as a program. Those methods check if the process has the rights to access the files.
Added: You can now change file rights for all user groups.