Fix some qdoc errors.

EnginioModel::enginio was renamed to EnginioModel::client.
EnginioIdentity::prepareSessionToken and removeSessionToken were moved
to protected section and qdoc thinks that they are apis.
Enginio was renamed to EnginioClient in QML.

Change-Id: I2549c9eac8d2ccbf8b82660eb92c4dcbd25dbb60
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Remove undefined EnginioReply ctor

The constructor is probably some leftover from an invalid conflict
resolution

Change-Id: I65431d7f90ce147703cbf6e48ad269b1ac12f388
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>