Refactor key point train for modularity, Add learning rate scheduler, Show Key Points

[mauritsreitsma]

One big commit, that should probably be multiple but I kinda missed commiting each step individually. Hope that is not a too big problem.

This is about making the training modular such that I can run training on a different machine and then validate on images locally with the trained model. Also adds visualization of the detected key points to the images.

[kekeblom]

Looks like great progress. Let us know how things develop on the keypoint detection front. Would make sense to start a log describing the experiments you have run and what the results were. Then slowly, we should be able to start narrowing down the issue and eventually fix it.