Wrong comment

## Description

The comments here are swapped (There are some other instances):

https://github.com/NREL/MoorPy/blob/master/moorpy/system.py#L1364

I suggest you to fix this adding some constants. e.g. on https://github.com/NREL/MoorPy/blob/master/moorpy/point.py#L4 you can add

```
POINT_TYPE_FIXED = -1
POINT_TYPE_FREE = 0
POINT_TYPE_COPUPLED = 1
```