Refactor export/import to remove technical debt

[joeribekker]

• Re-usable steps are definitely a problem
• Basically importing older forms in newer versions or vice versa causes various issues (e.g. form registration backends options: structure might change between versions and there's no mechanism to handle this currently).
• If you have deleted forms causes weird behaviour with the definitions that are used in deleted forms (merge conflicts)
• Maybe incorporate the DH thinking of moving forms from acc to prod?
• Sometimes you want private data in exports, sometimes not