Add logarithmic progress bar growth rate

[ryanelian]

There should be an option to make the progress bar grow logarithmic, as in it will never reach 100% but keeps on growing.

i.e. The progress bar grows toward 70% but slows down, making it never reach 100%.

[filkalny-thimble]

Logarithmic will reach 100%, it has no upper bound. What you want is something like x/(x+1), that just approaches 100%, never hitting it.