Support i18n in CC

This patch includes the code to introduce i18n into CC, contains:
(1). i18n init code
(2). Change the base controller to accept new HTTP_ACCEPT_LANGUAGE param
     which identifies the locale of request client
(3). Enhanced ApiError class to translate the error message for REST API
     response.

This patch does not include concrete REST API controller changes to
enable i18n. The changes of concrete REST API controllers' changes
will be submitted in other patches.
Fix missed renames

[#75217152]

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Use INDEX to refer to the worker index

[#69100160]

Signed-off-by: Luan Santos <lsantos@pivotallabs.com>
Ignore Delayed Job failures when failing jobs

Now that all jobs are wrapped with our exception catcher, we will
only look for cf api errors when marking jobs as failed.

[#76071892]

Signed-off-by: Luan Santos <lsantos@pivotallabs.com>
Renaming cc_service_broker_client to cc-service-dashboards in templates.
Remove redundant namespace

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Extract interchangable Dea/Diego backends

- Both backends have the same interface
- Also stop publishing the `droplet.updated` message since this was for the old HM
- [#76089928] & [#75217152]

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Space quota definitions can be read by space users

[#74628514]
Document fields that aren't required on update

[#76159766]
Add staging behavior to backends

Also fixes regression in a feature to properly migrate DEA staged
apps (without a start command) to Diego

[#75217152]
Refactor AppObserver - Use the Backend abstraction

[#75217152]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Update API docs to scope Quota Definition to an Organization

- update API DSL helpers to take title override
- base title default on path in list and get helpers
- base title default on model in delete helper

[#76311006]
Add ability to list spaces that relate to a Space Quota Definition

[#76159856]
Move dea advertisement subscription to stager_pool

[#75217152]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Remove unused method

[#75217152]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Add `docker_image` to app table, model, controller

API spec is updated with experimental support for docker images

[#75217152]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Avoid nil start commands when droplet is missing

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Allow service plans to be queried by service guid when not authenticated

[#76020926]
Extract classes into own files

[#75217152]

Signed-off-by: Peter Parente <pparent@us.ibm.com>
Make methods private where possible

Signed-off-by: Peter Parente <pparent@us.ibm.com>