Delete child services on service broker destruction

[Finishes #55912602]
Add ActiveRecord support for Delayed Job
Add API endpoint for job status

[#53927417]
Add delayed jobs rake tasks
Listen to CC queue in rake jobs task
Close ActiveRecord connection at the end of Thin thread
Setup environment before rake task
Clarify job status
Add guid to delayed jobs
allow users to access users in organization and spaces that they have access to
Fix mysql travis tests
Fix ActiveRecord postgres adapter
Fix travis postgres connection
Ensure every service plan has a unique_id

Originally, service plans were identified by their provider-label-name
tuple. Service brokers (formerly known as gateways) would use those values to
determine the desired plan when provisioning.

We introduced unique_id as a better way to uniquely identify plans (and
services). Our internal brokers use this unique_id attribute (though
third party brokers may not yet).

We want to encourage its use by requiring that Cloud Controller send it
with all provision requests, but we can't yet require that the broker
send it with catalog update requests. Until then, we'll generate a
default value.

[#55995896]
Destroy global domains after test
Allow brokers to set the service documentation_url

Updated the services#create specs to have a single, basic test that a
service is created and that a core set of allowed attributes is
persisted.
Merge remote-tracking branch 'origin/master' into loggregator_integration

Signed-off-by: Johannes Tuchscherer <jtuchscherer@pivotallabs.com>