Fix missing migration problem

There were two problems to solve here:

1) Database tables were not being created when loading the database from frontend. 

Because there wasn't a migration for the base set of tables, running `rake db:migrate` overwrote schema.rb and only loaded tables from engines. Vice versa, running only `rake db:schema:load` only loaded the contents of schema.rb and created no tables from the attached engines.

To solve this, the definitions from schema.rb have been moved to a migration.

2) A second problem was to ensure it was safe to run `rake db:migrate` from within frontend against an existing database already created from the old public_website sources (mimicking the situation with the live database).

The solution to this was to give the new migration in frontend the same timestamp as the last migration from public_website, so it would appear to have already been applied.