[nemo-qml-plugin-calendar] Add new Calendar API class
[nemo-qml-plugin-calendar] Wait for completion before populating AgendaModel
[nemo-qml-plugin-calendar] Give access to event exception times
[nemo-qml-plugin-calendar] Fix Qt 4 Compile

We use a define rather than a conditional based on QT_VERSION so
that moc understands it.