Progress bar

[k-doering-NOAA]

Suggested by Quang in JOSS review:

Due to long runtime, I recommend progress bars for run_SSMSE to inform users of elapsed and projected time. See the pbapply R package.

[k-doering-NOAA]

https://peter.solymos.org/pbapply/

This can probably be done when refactoring the parallel options (#152 ). In general, pbapply seems easy to add, but there is a note that it is a "little more complicated" for windows users. Also there is a note about the future backend: https://peter.solymos.org/pbapply/#working-with-a-future-backend