Matched Distribution: Not matched?

@cortes_c experienced that a particle tracking with a matched distribution doesn't remain matched after 1 turn. @baumgarten suggested to check the orientation of the integration.

Corresponding branch: https://gitlab.psi.ch/OPAL/src/tree/matched-gauss-fixes (deleted)

CC: @snuverink_j @cortes_c

fix crash of regression test (see !364 (merged))
~~check unit~~ [Edit: Checked with !393 (merged)]
check why not matched (see !393 (merged))
update regression test due to changes of !393 (merged) (see regression-tests!20 (merged))

Edited Jul 15, 2020 by frey_m