Save optimization output to .csv file

[GerbrichFerdinands]

Add the option to save optimization output to a .csv file.

asreview show trials.pkl prints the optimization output from the trials.pkl file to the screen.

This output can now be saved as a .csv file to a specified location by providing an extra argument, asreview show trials.pkl . or asreview show trials.pkl optimization_output for example.

@qubixes could you have a look?

[qubixes]

@GerbrichFerdinands Thanks! Some minor points:

• I think it makes more sense to either export it to a csv or print it to the console (not both).
• I would like to use argparse for the option to export. The preferred option flag would be -o/--output. I know I suggested this (temporary) solution, but it would be nice if we can extend it with more options at a later date as well.
• Also the filename of the export should be something you can supply to the command line interface.