Add reasonable defaults for NSSA Loss

[cthoyt]

Right now, the margin and adversarial_temperature parameters do not have a default for NSSA loss. We need to pick reasonable ones and set it.

[mberr]

From https://arxiv.org/abs/1902.10197, where this loss was proposed, they optimize these hyperparameters in the following ranges:

• self-adversarial sampling temperature alpha \in {0.5, 1.0}
• margin gamma in {3, 6, 9, 12, 18, 24, 30}.

The chosen parameters by the authors for FB15k, FB15k-237, WN18, WN18RR can be found at https://github.com/pykeen/pykeen/tree/master/src/pykeen/experiments/rotate :

dataset	alpha	gamma
FB15k	1.0	24
FB15k-237	1.0	9
WN18	0.5	12
WN18RR	0.5	6

So any of these configurations may be a good choice for a default value.