Path visualization improvements

1. Added `DynamicPath.resoltuion` property for setting the maximum step size, in seconds, to take when sampling a position for path visualization.
2. Improved position sampling to take steps more evenly.  For example, previously, if data was at 61 seconds steps, and resolution was 60.0, steaps would be taken at 0, 60 and 61.  Now they will be 0, 30.5 amd 61.