Updating the Migration::addPermission helper table name means we need
to move the seed migration to after the table rename migration. We also
add a sanity check for each permission's group since the foreign key
will fail if the group doesn't exist. Of course, the only way to make
sure groups are seeded before permissions is to move them into another
migration.
* Make filenames and order more consistent
* Split foreign keys into their own migrations, add statements to ensure
data integrity prior to adding them
* Add renameColumns helper, use other helpers where possible
This removes the funky auto-injection capability from migration
closures. While technically removing a feature, this means we do
not need a fully-wired IoC container e.g. during installation.
Instead, all migration closures simply receive a schema builder
object (which is what most of them were already doing anyway).
This will make it much easier for extension developers (and also less
error-prone) to create migrations for things like creating tables,
renaming columns and so on...
