eVlasiator initial pre-release

Release used in publication
Vlasov simulation of electrons in the context of hybrid global models: an eVlasiator approach, M. Battarbee, T. Brito, M. Alho, Y. Pfau-Kempf, M. Grandin, U. ganse, K. Papadakis, A. Johlander, L. Turc, M. Dubart, and M. Palmroth. Ann. Geophys. 39, 85–103 (2021)
https://doi.org/10.5194/angeo-39-85-2021