Option to disable anchors and just copy identical objects

[pxeger]

Currently, if an object containing the same list or dict object twice is dumped, aliases are created:

yaml = YAML(...)
x = [1, 2, 3]
y = [x, x]
yaml.dump(y, ...)

produces

- &id001 [1, 2, 3]
- *id001

It would be nice to have an option to disable this, so the output can be more easily readable, like this instead:

- [1, 2, 3]
- [1, 2, 3]

[smurfix]

While this should be possible, it's not as trivial as it seems, since you still need aliases when you dump recursive objects.