Migrate from Rails to ROM Sequel migrations

[christinach]

• Remove ActiveRecord::Migration.check_all_pending! Only verify DB connection
• Create new dir for the rom migrations
• Add new rake task for rom migrations: bundle exec rake rom:migrate
• Add rake task to fix auto-increment sequences on existing tables
• Convert Rails migrations to Sequel format migrations
• Add rake task to mark migrations that have already applied

ROM migration:

• uses Sequel.migration do instead of class ..< ActiveRecord::Migration
• we need to declare explicitly primary_key :id
• String instead of string - DateTime, Date instead of datetime
• Adds a new sequel_schema_migrations table

related to [#403]

when you checkout the branch:
lando destroy
bundle exec rake servers:start
RAILS_ENV=test bundle exec rake rom:migrate
bundle exec rspec

Also load the application locally and run some queries to make sure everything is working locally.

[christinach]

In order to run the tests successfully please run:
RAILS_ENV=test bundle exec rake rom:migrate
and then
bundle exec rspec

[christinach]

We want to run this rake task for a 1st time setup. I ran it on staging when I deployed with capistrano this PR.
We should keep it for when we run it in production for the first time.
After that it is safe to remove it.

[christinach]

I renamed the migrate directory that has the Rails applications in case we need to compare something between the rails and rom migration files.
After that it is safe to remove it.