HydroChrono 0.2.8 - Fixes for gcc compilation and wave kinematics

This patch fixes the following issues:

• Fix compilation issue with gcc for demos (+ explicitly include <algorithm>)
• Add wave stretching option for regular waves
• Deep water check done with a common function (condition k*h>89.4 to be considered deep water)
• Wheeler wave stretching done with a common function, and corrected when mwl=/=0