1. Added command-line arguments:

    1. -f to use a different filename (<string>)
    2. -s to automatically save each <int> updates
    3. -dts to set the delta-time scale
    4. -cdt to set the constant delta-time (overrides -dts)

    Note: README.md says -min is implemented, but it is not, yet.

2. General bug-fixes.

    1. Zooming with high delta-times. DTs are now separated into program-dt (used when variable dt is on) and constant DT, only used when variable dt is off and only used by the simulation, not the UI.