[TIMOB-3035]iOS: EventKit module

EventKit module contains:

** Basic Calendar fetching and reading all of its properties. 
** Accessing, modify and delete events.
** Create , update alerts
** Create, delete recurrence rules for events.

There are some sample code for testing within the documentation.
Detailed testing code will be provided along with [JIRA TICKET](https://jira.appcelerator.org/browse/TIMOB-3035)