Output the correlation time for the bias instability model

[shalabymhd]

To be able to use the bias instability model, the correlation time is required, which is currently being recorded in the code but not logged. The main change in this PR is to simply add the bias correlation time to the terminal output. Another change I made is to log the terminal output to a output.log file, as I found myself rerunning analysis.py over and over, when they could have just been logged the first time. Thank you!