PEP8 naming

__init__.py

assignment.py

assignment_collection/__init__.py

assignment_collection/assignment_collection.py

assignment_collection/simplifications.py

astnodes.py

backends/__init__.py

backends/cbackend.py

backends/dot.py

backends/logging.json

backends/simd_instruction_sets.py

boundaries/boundaryhandling.py

boundaries/createindexlist.py

boundaries/inkernel.py

cpu/__init__.py

cpu/cpujit.py

cpu/kernelcreation.py

data_types.py

datahandling/serial_datahandling.py

display_utils.py