Introduce EnginioModel::reload

[ChangeLog][EnginioModel] Added reload() function to
EnginioModel to force a refresh of all model data.

Change-Id: I7b1a3fdd6e63950f5494d4bab8511feb9f80d9fb
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>