Completion of the AMR interface

The following tasks have to be completed:

• Mergen of the fork https://gitlab.psi.ch/frey_m/src into the OPAL master (see !312 (merged))
• Add file header according to #482 (closed) to AMR solver classes (see !313 (merged))
• Add file header to new AMR classes in Ippl (see !314 (merged))
• Update of the OPAL manual (see https://gitlab.psi.ch/OPAL/documentation/manual/merge_requests/32)
• AMR regression tests (see regression-tests#78 (closed))
• Documentation of the septum objective of the optimiser (see https://gitlab.psi.ch/OPAL/documentation/manual/merge_requests/33)
• Test of the septum objective? Edit: Moved to regression-tests#83.