Some minor internal and API fixes

src/pystencils/__init__.py

src/pystencils/alignedarray.py

src/pystencils/boundaries/boundaryhandling.py

src/pystencils/datahandling/serial_datahandling.py

src/pystencils/display_utils.py

src/pystencils/runhelper/db.py

src/pystencils/simplificationfactory.py

src/pystencils/sympyextensions/integer_functions.py

src/pystencils/utils.py