Velocity and geometry units added to output files.

[JanosJiri]

The units of geometries and velocities are lacking in their respective output files. I've spent time looking for the right units of velocities in ABIN several times (because I always forget) and others in Prague have the same issue. I suggest to add the units of geometries and especially velocities to their respective output files.

The proposed way adds the units to every single geometry/velocity such that if someone greps specific geometries/velocities, the information about the unit is kept. Alternatively, the unit could be added to a header, but this would add one extra line and could break loads of existing scripts grepping from movie.xyz or velocities.xyz. What I propose is left for discussion @danielhollas , but adding this would save a lot of time for many people.

FYI, all the tests are failing because of the added units to the files but I did not mend the tests before (or if) we agree on the precise way of adding them.

[danielhollas]

Thanks! I basically agree with all you wrote, and the approach looks reasonable. I'll think a bit more about the wording/ formatting later today.