Add first sorting algorithm: Quicksort

I have added the first sorting algorithm, an inefficient implementation
of Quicksort.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add merge sort algorithm

I have added the next sorting algorithm, an inefficient variant of the
merge sort sorting algorithm.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>