[nemo-qml-plugin-email] Run next offline action when in offline mode and current action is online.

When in offline mode, if current action requires network, we try to
run all offline action in the queue in the meantime.
[nemo-qml-plugin-email] Add EmailAction::operator!=()
Merge pull request #109 from nemomobile/offlineActions

[nemo-qml-plugin-email] Run next offline action when in offline mode and  current action is online.