Alternating Flexing Battery Holder

I somewhat hoping for a remix of "customizable alternating orientation" but to this day there are none.

I finally got the motivation to do such remix where there's an option to do alternating orientation to have a serial battery setup and also keeping the old orientation for Parallel setups.

Credits to
- [enif](https://www.thingiverse.com/enif/designs) for the initial customizable battery holder.
- [nhorvath](https://www.thingiverse.com/nhorvath/designs) for the alternating calculations