Improve display of tick labels on the timeline

The timescale in the timeline should show ticks and tick labels as they appear in scientific plots, i.e:

• Instead of using the format HH:MM:SS.mmm, the timeline should show the values in seconds.
• The labels should have minimum width.
• Integer values or real values ending in 0 should be preferred.

For instance, if the minimum value to be shown is 1.04, the maximum value is 2.27, and the axis must have 6 ticks, then they should be placed at 1.2, 1.4, 1.6, 1.8, 2.0, and 2.2 (and not 1.1, 1.3, 1.5, 1.7, 1.9, and 2.1, nor 1.05, 1.25, 1.45, 1.65, 1.85, 2.05, 2.25)

For implementation ideas, see the Wilkinson’s algorithm and the comments in issue #394 of the ScottPlot project.