Companion changes required for integration with my CASinoCore Pull Request

The following is a set of changes to CASino that are required for integration with my CASinoCore Pull Request (rbCAS/CASinoCore#12).

The biggest changes are in the `casino:install` generator script.

This gem is now the owner of the required database migrations. Running `casino:install` will copy over the migrations into the host Rails application. The end-user must then run `rake db:migrate` to finish the installation.

In order to more closely match how a Rails Engine is expected to work, the database table names are now namespaced with `casino_`. Since the rbCAS team is already running CASino in production, I have added a migration generator that will create a database migration that will rename all of the tables and recreate all indexes to match the new naming scheme.

**I would highly recommend thoroughly testing this behavior before pushing to production.** It passed Works For Me status, but that only goes so far when dealing with a currently running production system

The installation generator will automatically detect the older syntax and will prompt the user that this migration is required and will ask if it is OK to run that particular script.

**Note:** Before merging, I'll need to revert a change in the `Gemfile` so that it no longer points to my branch.