Scope out additional loss functions

[AnzeXie]

Is your feature request related to a problem? Please describe. Currently, the supported loss functions we have for Marius are SoftMax and RankingLoss.

Describe the solution you'd like We can expand the set of loss functions by implementing additional loss functions to Marius. We can implement losses into 2 new source files: loss.cpp and loss.h. We can also add a new section in the configuration for loss options.

We can use the loss functions implemented by PyKeen as a reference: List: https://github.com/pykeen/pykeen#losses-7 Implementation: https://github.com/pykeen/pykeen/blob/master/src/pykeen/losses.py Documentation: https://pykeen.readthedocs.io/en/stable/reference/losses.html

[JasonMoho]

We should add a new doc page and describe each loss function in it and also update the configuration documentation.