Rename cron_time_zone to cron_timezone. Separate add_concurrent_foreign_key.

app/models/ci/trigger_schedule.rb

app/validators/cron_timezone_validator.rb

app/validators/cron_validator.rb

db/migrate/20170329095907_create_ci_trigger_schedules.rb

db/migrate/20170404163427_add_trigger_id_foreign_key.rb

db/schema.rb

lib/gitlab/ci/cron_parser.rb

spec/factories/ci/trigger_schedules.rb

spec/lib/gitlab/ci/cron_parser_spec.rb

spec/lib/gitlab/import_export/safe_model_attributes.yml

spec/models/ci/trigger_schedule_spec.rb

spec/workers/trigger_schedule_worker_spec.rb