Saving checkpoint before and after swa

[davkovacs]

No description provided.

[davkovacs]

This pull request implements the following:

• save the model with lowest validation loss both before and after swa
• evaluate both of the best models at the end of the training
• save both models as .model at the end of the training
• restart latest from swa checkpoint if present

[davkovacs]

There are two more bugs to be fixed before merging:

• when the second checkpoint (swa checkpoint) is loaded it throws error because of model and data not being on the same device ???
• The swa learning rate flag seems to be ignored.