Add more fractals

[comodoro]

Preliminary add more fractal classes, either not resource demanding to com.draabek.fractal.canvas.instance, or GLSL ones to assets/*.glsl

[haythamnikolaidis]

Hi I can add a Koch Snowflake implemented in Java.

[comodoro]

Inspiration: https://math.stackexchange.com/questions/1099/mandelbrot-like-sets-for-functions-other-than-fz-z2c