[management-api] Make a clear distinction between primary_owner and owner

[brasseld]

As of today, primary_owner and owners of an api / application can achieve exactly the same actions.

As the primary_owner is the "creator" of the entity, he must have more rights than owners.
A good idea will be to limit actions to this particular role. Limited actions could be:

• Delete an API / application
• Change primary_owner of the API / application

[brasseld]

Must be closed by: #176

[brasseld]

Update the UI to:

• Disable or remove Delete button when authenticated user is not the primary_owner

[brasseld]

Updating context-path is an exclusive action for the primary_owner : #203

[brasseld]

Already implemented