Allow configuring and managing registry database

HELP

...ts/0016_container_registry_supports_metadata_database.yml

doc/howto/registry.md

gdk.example.yml

lib/gdk/command.rb

lib/gdk/command/import_registry_data.rb

lib/gdk/command/registry_database_manager.rb

lib/gdk/command/reset_registry_data.rb

lib/gdk/config.rb

lib/gdk/diagnostic/registry.rb

spec/lib/gdk/command/import_registry_data_spec.rb

spec/lib/gdk/command/reset_registry_data_spec.rb

spec/lib/gdk/config_spec.rb

spec/lib/gdk/diagnostic/registry_spec.rb

spec/support/templates/registry/config.yml.erb_spec.rb

support/bootstrap-registry-db

support/import-registry

support/makefiles/Makefile.postgresql.mk

support/makefiles/Makefile.registry.mk

support/migrate-registry