Refactorings 22 (#3189)

* removed unused variable

* static imports, this, final

* simplified data structure

* static imports, final, this

* renamed variables, replaces class with lambda

* removed unused methods, renamed method, rewritten method in functional style

* moved BitSet to ...user package as it is only used by DataverseRole class, made it package private

* manual formatting

* removed unused method, optimized comparator not to allocate Long(0)

* added bitsValue to Permission

* improved performance of permission checking

* refactored BitSet out, removed BitSet

* introduced permission streaming method

* comments addressed

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Co-authored-by: lbownik <lbownik@icm.edu.pl>

Author: lbownik