Add percentage to CB-Geo MPM's output
This MR adds the percentage to the line output during the simulation. Here is an example:
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[2023-07-07 13:43:32.766] [MPMExplicit] [info] Step: 6400 of 8000 (80%).
[2023-07-07 13:43:32.771] [MPMExplicit] [info] Step: 6480 of 8000 (81%).
[2023-07-07 13:43:32.776] [MPMExplicit] [info] Step: 6560 of 8000 (82%).
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The percentage printed will always be a floored integer, so verbosity=nsteps/100
gives the best resolution possible.