First release

This is our first release of the caldav framework.

It provides the following features:

• Abstractions for VCALENDAR, VEVENT, VTODO
• Client to connect to a caldav server
• Enums for various property values defined in RFC5545
• Automatic timezone handling based on PHP DateTime and DateTimeZone objects including Day Saving Times.
• Abstractions for various property types defined in RFC5545