Migration option to allow skipping existing tables check

This can be an option in the API call and on the app console UI. Something like Allow existing tables or the like.

What this will do is the following:

• Skip the existing tables check that happens at the start of the migration.
• Check if the new element exists before creating it
• If the table exists, do a diff on it and see if it is different and:
  • If it is different, throw an exception and bail out because we can't migrate a table when we don't know what version it is at and figuring out where it should be is too difficult.
  • If it is the same, celebrate by carrying on like nothing happened.