Consistency in Identifier fields

[kulmann]

At the moment the fields in the Identifier message type are:

• extension
• bundleKey
• settingKey

As proposed here #28 we could decide to drop the Key suffix. This has effect on several repositories:

• ocis-settings: change protobuf, handlers and manager. regenerate api client and change ui code referencing the new identifier
• ocis-accounts: change registering settings bundles to new identifier
• ocis-hello: change registering settings bundles to new identifier
• owncloud-sdk: copy the regenerated api client from ocis-settings into the vendor dir and adapt code to new identifier

[kulmann]

Solved in ocis-settings, ocis-accounts, ocis-hello, owncloud-sdk and phoenix