Removes pin to message_broker_producer module to now use latest release

**Not ready for merge, discussion only**

Fixes #3239

The `message_broker_producer.module () has been updated to v0.2.0. `dosomething_mbp,module` needs to updated to integrate the new functionality.

- [ ] "Unpin" release version in `drupal-org.make` by removing:
```
; Pin to 0.1.21+aug25 pending 0.2.x development
projects[message_broker_producer][download][revision] = "40e8d9892e378846adf5cb9b295f53c8a533f123"
```
- [ ] Add `hook_update` function to `dosomething_mbp` to create `message_broker_producer` production entries. The "production" entries will define exchange, queues and routing_keys values for each production specific to the $origin value defined in the `dosomething_mbp_request()`.
- [ ] Update `dosomething_mbp.module` to call `message_broker_producer_request(<production>, <payload>)` where <production> referers to the values defined in the `dosomething_mbp.module - `hook_update()` function.
  - [ ] Update `dosomething_mbp_request()` to define the `$production` value based on the values defined in the `dosomething_mbp.module - `hook_update()` function.
  - [ ] Update `dosomething_mbp_get_transactional_payload()` to define Mandrill templates in payload based on $origin.
  - [ ] Update `dosomething_mbp_get_transactional_payload()` to define Mandrill tags in payload based on $origin.

- [ ] Refactor `mbc-transational-email` to use Mandrill template value in message payload rather than in logic in the consumer : https://github.com/DoSomething/mbc-transactional-email/blob/master/mbc-transactional-email.php#L114-L143
- [ ] Refactor `mbc-transational-email` to use "tag" value in message payload rather than in logic in the consumer : https://github.com/DoSomething/mbc-transactional-email/blob/master/mbc-transactional-email.php#L114-L143