tgDataLogger2 should sort its senseables by position

[apsabelhaus]

Currently, the log file from tgDataLogger2 does not have any ordering of the sensors. Similar with names: we don't currently enforce any named ordering, so the 1,2,3,... naming of rods etc is arbitrary.

However, for compounds, we need to know which compound (which tags) correspond to which compounded rigids. This is especially true since compounds have random tags associated with them (another bug: these don't seem to be seeded properly.)

SO, maybe we should add a required method to tgSenseable, which outputs some ordering. That way, tgRigidBody could order by (for example), X position, then Y, then Z. Should be an easy sorting within the data logger.