Version bump for 5.6 (#543)

* Version bump for 5.6

* Update CHANGELOG.md

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Co-authored-by: Robert Speck <pancetta@users.noreply.github.com>

Small refactor of spectral helper to prepare for 3D (#541)

TL: bump version to 5.5.2 + added release guide for maintainers (#489)

* TL: added release guide

* TL: additional detail

* Update 07_release_guide.md

* TL: minor correction on release guide

* TL: typo

* TL: lighter testing

* TL: bump version to 5.5.2

* TL: let's not care

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Co-authored-by: Robert Speck <pancetta@users.noreply.github.com>

TL: dump version (#474)

Merge branch 'master' of https://github.com/Parallel-in-Time/pySDC

version bump

Merge branch 'master' of https://github.com/Parallel-in-Time/pySDC

Bump version

proper readme and link

NCCL communicators (#392)

* Added wrapper for MPI communicator to use NCCL under the hood

* Small fix

* Moved NCCL communicator wrapper to helpers

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Co-authored-by: Thomas <t.baumann@fz-juelich.de>