Add logarithmic and ln functions

[ChrisLow556]

It doesn't recognize ln(x-1) or log_e(x-1) when i typed it in

[ChristopherChudzicki]

Hello! The natural logarithm on math3d is log(x).

ln(x) will be a synonym for log(x) in an upcoming version. Probably won't add subscripts for bases in the near future (harder for the mathematical parser). But you can use the rule log_b(x) = log(x)/log(b).