2-step deployment with ->deploy_shadows() w/ prelim test

Added deploy_shadows() method to Schema::Shadow to be able to deploy
only the shadow sources.

Added non-shadowing test schema TestSchema::SakilaPlain for testing
creating and deploying a database before adding shadowing to it. Added
t/deploy_shadows.t which tests the deploy() and subsequent
deploy_shadows() calls, but doesn't try to make any actual row changes
yet.

Also regenerated both Sakila and new SakilaPlain schemas with custom
base result class