Using fprettify to format processed sources

See merge request ces/hpc-for-es-team/AutoRPE!25

Bugfix to save variable declaration with class Variable

See merge request ces/hpc-for-es-team/AutoRPE!24

Added testcase lorenz

See merge request ces/hpc-for-es-team/AutoRPE!23

* Added automatic tests for each new case added there.
* Moved tests from unittest to pytest.
* Fixed old failing tests.
* Fixed some issues that arose when trying to use ImplementRPE with simple dummy codes: Where to add the additional use rp_emulator.
* Added an extra pre-processing step to replace all variable definitions that used the traditional style (without ::).

Changes for NEMO 5

See merge request ces/hpc-for-es-team/AutoRPE!22