*clarify help text and squash migrations
*adds new internal_limit field to Job model for faster reference
*if field is non-blank, populate shard params in summary_fields
*add summary information to UI job/wfj details, JT selector
*allow sharding with prompts and schedules
*modify create_unified_job contract to pass class & parent_field name
*make parent field name instance method & set sharded UJT field
*access methods made compatible with job sharding
*move shard job special logic from task manager to workflows
*save sharded job prompts to workflow job exclusively
*allow using sharded jobs in workflows
it looks like choices can also be a list and _maybe_ comma delimited;
clearly there's a lot of history here; let's verify and test what's _really_ supported and _then_ add any necessary validation
this commit implements the bulk of `awx-manage run_dispatcher`, a new
command that binds to RabbitMQ via kombu and balances messages across
a pool of workers that are similar to celeryd workers in spirit.
Specifically, this includes:
- a new decorator, `awx.main.dispatch.task`, which can be used to
decorate functions or classes so that they can be designated as
"Tasks"
- support for fanout/broadcast tasks (at this point in time, only
`conf.Setting` memcached flushes use this functionality)
- support for job reaping
- support for success/failure hooks for job runs (i.e.,
`handle_work_success` and `handle_work_error`)
- support for auto scaling worker pool that scale processes up and down
on demand
- minimal support for RPC, such as status checks and pool recycle/reload
