[quicksort] Initial implementation
[quicksort] Change notation, use word "list" instead of "sequence"
[quickselect] Initial implementation of the quickselect algorithm
[quickselect] Change notation, use the word "list" instead of "sequence"
[quickselect] Change notation, use the words "begin" and "end" for indices

Changed from using the words "left" and "right"
[quickselect] Update docstrings and some comments
[quickselect] Add option to select over part of the list
[quickselect] Fix bug "wrong parameter order in recursive calls"
[quickselect] Add some checks, plus minor code format changes