Update asset structure with webpacker gem

Refactor how Template upgrade customization works (#1856) ...

* Refactor how Template upgrade customization works

- Added position_in_parent to child-records Phase, Section, and Questions
- Extracted upgrade_customization! into its own service object

wip: rebasing on development

wip: pushing to Ghub

wip: Template upgrade customisation service working

Add migration to update versionable_id for records

* Fix bug in org swaps test

Test was failing because JS wasn't executing fast enough in test browser

* Refactor how locales are set in specs

* Fix bug in plan exports caused by git merge

The routes weren't merged properly which seems to have caused a regression error

* Add documentation for SectionSorter

* Update rubyzip and re-instate Bundle Audit

This was disabled because it was failing the Travis CI script. Since there wasn't a
new version of the rubyzip gem to upgrade to, we couldn't turn the error off.

* Add length constraints to versionable_id

* Add length constraints to versionable_id

* Fix bug in ActsAsSortable module

... I have no idea why those issues haven't popped up before now!?

* Fix random bug in I18n

* Move versioning ID migration into own rake task

Add schema structure to factories files

Remove published column from sections table ...

This was no longer required, and caused a bug when trying to create a new section.

Adding fixtures