Disable unused imports.
Prepare flatten_psi_tables and _generate_psi_name for avg table generation.
Preparations for new avg state in unoptimized create_argument and create_function.
Preparations for new avg state in optimized create_function and create_argument.
Preparations for avg features in quadraturetransformerbase.
Preparations for avg features, generation of avg tables (disabled).
Pass avg argument around in quadrature transformers.
Enable cell_avg and facet_avg generation.
Merge branch 'martinal/topic-avg-operators'
Update changelog.