[Feature] Functionality to control amount of whitewater generated by an Obstacle object

[rlguy]

This feature will allow the user to control the amount of whitewater generated by an obstacle object. This feature will be included in the next version update (1.0.5).

This feature has been added as a parameter in the Obstacle object settings panel:

For example, a whitewater influence value of 0.5 will generate half the amount of whitewater, a value of 2.0 will generate double the amount of whitewater.

Alternatively these values can also be set for each object in the Whitewater settings panel:

[rlguy]

Added this to Obstacle documentation: https://github.com/rlguy/Blender-FLIP-Fluids/wiki/Obstacle-Object-Settings