Delete bank gen and old kernel
Changes
This MR deletes bank gen and the defunct 'spiir' kernel, repeating changes from !226 (closed).
Bank generation is still useful, but for now it will be run offline on clusters which allow Py2. Upgrading the pipeline is higher priority, and the original code is still available in other branches.
I think gstlal-spiir/python/workflow is also related to bank generation, and may safely be deleted. For now I'm leaving them as-is, but if reviewers prefer I can remove them too.
Purpose
I intend to split !226 (closed)'s changes into a number of MRs, which won't be functional code versions themselves, but once complete will encompass the full set of changes to upgrade to py3.
This should provide useful code diffs for reviewers.