[nemo-qml-plugin-calendar] Use notebook color if specified

Previously if no setting for the notebook color was defined, the
notebook would be colored randomly.  This commit ensures that if
no explicit setting for the notebook color was defined, it should
instead attempt to use the color specified by the notebook, and
only if that is empty, to fall back to the randomly generated
color.
Merge pull request #7 from chriadam/master

[nemo-qml-plugin-calendar] Use notebook color if specified
Merge pull request #8 from aaronkennedy/master

[nemo-qml-plugin-calendar] Always convert to local timezone for display
[nemo-qml-plugin-calendar] Always reset reminder
Merge pull request #9 from aaronkennedy/reminders

[nemo-qml-plugin-calendar] Always reset reminder
[nemo-qml-plugin-calendar] Support converting event to vCalendar

This commit adds an invokable function to the NemoCalendarEvent type
which returns the vCalendar representation of the event as a string.
This is useful for sharing the event.
Merge pull request #10 from chriadam/vcalendar

[nemo-qml-plugin-calendar] Support converting event to vCalendar
[qmldir] Add Module Identifier Directive
Merge pull request #11 from thp/module-identifier-directive

[qmldir] Add Module Identifier Directive
[nemo-qml-plugin-calendar] Coalesce AgendaModel queries