Adjust whitespace
[nemo-qml-plugin-calendar] Protect event cache against null events

Creating event to an excluded notebook triggers reloading content,
at which point calendar doesn't anymore include the newly created event.

Made cache refuse to replace kcalcore event with null instance.
Merge pull request #21 from pvuorela/master

protect against null event pointers
[nemo-qml-plugin-calendar] Notebook management related changes.

 - Add calendar uid property to event. Required by qml to select notebook for saved event.
 - Fix event::realonly to return notebook readonly status where event is stored.
 - Change event:save to require notebook uid. Enables moving event to other notebook.
 - Fix missing colorChanged signal emit.
 - Add readonly role to notebook model.
 - Add localCalendar role to notebook model.