Create quicksort.php

An implementation of Quicksort from Coursera's lectures.
pivot=0 means first element as a pivot
pivot=1 means last element as a pivot
pivot=2 means median element as a pivot
Results:
For file:10.txt and pivot 0 m=25
For file:10.txt and pivot 1 m=29
For file:10.txt and pivot 2 m=21
For file:100.txt and pivot 0 m=615
For file:100.txt and pivot 1 m=587
For file:100.txt and pivot 2 m=518
For file:1000.txt and pivot 0 m=10297
For file:1000.txt and pivot 1 m=10184
For file:1000.txt and pivot 2 m=8921
For file:QuickSort.txt and pivot 0 m=162085
For file:QuickSort.txt and pivot 1 m=164123
For file:QuickSort.txt and pivot 2 m=138382