Change number of points slider to use a log scale and some other small cleanup

[alexprand]

This contains some minor tweaks I made a couple months ago while thinking about other (hopefully more interesting) things to do.

The main functionality change here is to change the number of points slider to use a log scale. With the current linear scale, it is hard to adjust the number of points when users want the number to be relatively small (say in the hundreds) but the user has pretty good control over mostly irrelevant differences in the number of points on the larger end of the spectrum (i.e., 40k vs 42k points is mostly irrelevant but easy to control). You can try out the different behavior and decide if you think it is more intuitive.

The other two commits are just minor cleanup and changes I made in the process of poking around in the code.