adjust limits of hadron cut

FLUKA minimal energy is 20 MeV. this should be reflected by the minimum hadron cut value in the EAS application.

changed milestone to %Beta Release

added Easy First Issue Hadronic labels

marked this issue as related to #664 (closed)

created branch 723-adjust-limits-of-hadron-cut to address this issue

mentioned in merge request !655 (merged)

assigned to @riehn

mentioned in commit f23cef42

closed with merge request !655 (merged)