Replace Secret with Key in methods name

For the sake of consistency we have changed the names of few helper methods:
ConnectionString.CreateUsingSharedAccessSecret is now changed to ConnectionString.CreateUsingSharedAccessKey
ConnectionString.CreateUsingSharedAccessSecretWithFullAccess is now changed to ConnectionString.CreateUsingSharedAccessKeyWithFullAccess
ConnectionString.CreateUsingSharedAccessSecretWithListenAccess is now changed to ConnectionString.CreateUsingSharedAccessKeyWithListenAccess