Improve the training scripts

[jbirkesteen]

The training scripts are a bit messy. The following improvements (some to functionality, some to documentation) would be a good place to start.

• [x] Function arguments should be clear, and the regular training script and self-training script should not be too different from eachother
• [x] Make the usage of benchmarking functionalities clear
• [x] Give user control of filenames
• [x] Implement saving networks based on their benchmark performance
• [x] Format percentage completed message
• [x] Print "Benchmarking..." to console