[INTERNAL] Algorithms: added assertions in maxElement() and minElement()
[FIX] StringSet: check empty StringSet in maxLength()
[API] StringSet: added minLength()
Merge branch 'fix/algorithms' into develop

* fix/algorithms:
  [API] StringSet: added minLength()
  [FIX] StringSet: check empty StringSet in maxLength()
  [INTERNAL] Algorithms: added assertions in maxElement() and minElement()