Now Libuipc support both newton min_iter and max_iter

[MuGdxy]

In d0615d9, we support a minimal iteration limit for non-linear Newton.

config = Scene.default_config()
config['newton']['min_iter'] = 1 # default 1
scene = Scene(config)

You may ask why we need it.

The scenario may be:

Now you have a relatively large convergence tolerance, the non-linear Newton will likely stop at the 0-th iteration, cuz the external force is not large enough to create a vertex-displacement large than the tolerance, the object tend to be static. You can set min_iter to 1 to make some difference. But in the other side, sometimes, you perfer a more static behaviour, that tiny force or numerial error should not influence the motion, then you can set the min_iter to 0.

The default min_iter is 1.