movement data class

[roaldarbol]

Think of how to what a movement class should be able to include. It will likely link to #19, so attributes are parts of the data set. I'm a bit enticed by sf and their sf class, that uses a standard (XYZM), and there are method associated with certain classes.

Thinking onwards from XYZM standard, the movement structure could maybe be described as TKXC/TKXY/TKXYZ where T is time, K is keypoint and C is certainty (probably there's a better term, just can't remember it right now). The class could then have a Dimensions tag, which would be X/XY/XYZ.
https://gis.stackexchange.com/questions/39131/what-is-an-xyzm-measurement-model