* core: gb refactor

* Work on gb test

* Testsuite: Gay Berne pair potential (no forces/torques)

* Core: Apply corrections suggested in #2229 to forces/torques

* GAY_BERNE depends on EXPERIMENTAL_FEATURES

* Testsuite: Gay-Berne,  avoid dipole hack to set orientation

* Formatting

* Testsuite: Fix gb energy test (ia deactivation)

* Testsuite: Gay-Berne on 3 cores and silent