Clearly define the proper permissions for screwdriver admin and user

[yakanechi]

What happened:
Screwdriver admins have strong permissions enabling them to delete pipelines which has not permissions within the repository.
This is necessary so that admins can delete the original repository of the pipeline should it be deleted.
On the other hand, if a child pipeline's repository has been deleted within an external configuration pipeline, even an screwdriver admins cannot delete the pipeline via the UI because it cannot be set to inactive in the UI..

Furthermore, whilst possessing powerful privileges, screwdriver admins cannot disable jobs in any pipeline via the UI.
This means they cannot halt problematic jobs that run periodically.

What you expected to happen:

The minimum permissions truly required for screwdriver admins are defined.
The following are related:

How to reproduce it:

[yakanechi]

We have discussed this matter as a team.

The following permissions should be newly granted to sd-admins:

• Stop build
• Job enabled/disabled
• Switch CheckoutURL
• Sync pipeline
• Clear cache
• Delete the active child pipeline of external-config

[minghay]

@yakanechi Related to job enable/disable, it would be nice to have a new option to disable a pipeline. Disabling a pipeline would allow sd-admins to help save resources for pipelines that may not be needed, or temporarily stopped from executing any builds for certain reasons, but not ready to be deleted.